Everyone wanted it to happen except for the Giants, or at least it seemed that way. San Francisco finally called on top prospect Buster Posey today, and will start him at first base against the Diamondbacks tonight. He’s best known as a catcher and he’d provide the most value to the team from behind the plate, but for fantasy purposes, the more first base Posey plays, the better.

It’s Fantasy 101: he has catcher eligibility but will play at least part of the time at a less demanding position, which translates not only more at-bats in general, but (theoretically) better offensive production given the decreased wear and tear. It’s a win-win.

The Florida State product simply annihilated the minors during his season-plus stint there, racking up a .333/.427/.552 batting line in 750 plate appearances, almost all of them while squatting behind the plate. Baseball America ranked Posey as the 7th best prospect in the game coming into the season, calling him “a pure hitter with terrific strike-zone awareness, and his clean, unfettered swing allows him to drive pitches from pole to pole,” though they acknowledge that power isn’t his game. It’s not hyperbole to say he has the best plate approach of anyone in the organization, big leagues included.

CHONE projects a .329 wOBA in 2010, while ZiPS pegs him for .333. Both of those obliterate the .309 wOBA starting catcher Bengie Molina has put in 40 games this year, nevermind the .308 wOBA he fashioned last season. His homerun power might be minimal at the outset considering his home park and some of the parks in the NL West, but Posey should contribute solid AVG and OBP (if your league counts that) while surely chipping in a few RBI as well.

Posey is owned in just 15% of Yahoo! leagues, and right now he’s only eligible at catcher. He’ll pick up 1B eligibility in a week or so, and while it’s not terribly important, a little flexibility never hurt anyone. If your struggling to find production from the catcher’s spot – perhaps you’re stuck with an injury fill in like Francisco Cervelli – then there’s probably no better option on the waiver wire right now.

Pittsburgh Pirates placed 1B Steve Pearce (ankle) on the DL; recalled UTIL Neil Walker from Triple-A Indianapolis.

The ankle injury is a tough break for Pearce, as the 27-year-old was beginning to get some big league playing time with Jeff Clement (.235 wOBA) flailing at the plate. Still, Pearce is basically a first base-only player who likely doesn’t have the bat to hold the position. The Pirates experimented with him in the outfield, but the 5-11, 200 pounder doesn’t cover much ground. The former South Carolina Gamecock owns a career .281/.354/.482 triple-slash at the Triple-A level, and his ZiPS projection (.269/.336/.455, .345 wOBA) is a little light for first base. He’s the new Chris Shelton.

Walker, meanwhile, is trying to revive his prospect status after all but falling off the map. The 11th overall pick in the 2004 draft began his career as a catcher, but was shifted to third base prior to the 2007 season. The 6-3, 215 pound switch-hitter turned in modestly productive offensive numbers in A-Ball, given that he was behind the dish at that point:

Low-A South Atlantic League (2005): .301/.332/.452, 3.9 BB%, 15.7 K%, .151 ISO
High-A Carolina League (2005-2006): .281/.331/.402, 5.6 BB%, 17.3 K%, .121 ISO

Baseball America ranked Walker as the #81 prospect in the game prior to 2005, #43 before 2006 and #74 leading up to the 2007 season. Before ’07, BA said that Walker’s power was muted in 2006 by a surgically repaired left wrist, but claimed he had “the potential to hit 30 home runs a season.” They did caution that he lack of patience could become an issue in the upper levels of the minors, and that Walker’s D behind the dish was a work in progress. “The Pirates might get more long-term production out of him,” BA said, “by shifting him to another position, and he has the athleticism to handle third base or the outfield.”

In ’07, the Bucs did move Walker to the hot corner, and he batted .277/.349/.434 in a season spent mostly at Double-A Altoona. His power improved somewhat (.157 ISO), and happily, he stopped hacking so much. Walker walked in 9.8 percent of his plate appearances, whiffing 17.4 percent. Baseball America again named him a top 100 prospect, placing him at #61 before the 2008 season.

The next two years of Walker’s career wouldn’t be nearly as sunny. At Triple-A Indianapolis, he batted .242/.280/.414 in 2008 and .264/.311/.480 in 2009. Walker popped some extra-base hits, with a .172 ISO in ’08 and a .216 ISO in ’09, but his plate approach was lousy. He drew ball four just 5.3% and struck out 20.2% in ’08. In ’09, he walked 6.7% and K’d 15.4%. Walker also missed time last year with a sprained knee and a broken pinky. The Pittsburgh native made his big league debut last September, but it was with considerably lower expectations than when the Pirates called his name back in 2004.

Prior to 2010, BA ranked the perennial top-100 prospect as just the 26th-best farm talent in Pittsburgh’s system. His scouting report was blunt: “he undermines his offensive potential by lacking plate discipline…Walker has expressed a willingness to become a super-utility player.” That, said BA, “may be his ticket to having a big league career of any length.”

With Indy this season, Walker has roamed around the diamond. He has logged time at first, second and third base, while also manning left field. He put up a .321/.392/.560 line in 189 PA. A .360+ BABIP certainly helped, but Walker posted a .239 ISO, walked 10.1 percent of the time and whiffed 18.5 percent.

ZiPS projects Walker to bat .259/.304/.439, with a .325 wOBA. His future in Pittsburgh remains hazy, though — Pedro Alvarez is going to man one of the infield corners in short order. And While Andy LaRoche will never be a star-caliber talent, he did post a 2.6 WAR season in 2009. If Alvarez takes over at third, LaRoche could be shifted to second base. Should Pedro play first, Walker could enter the picture at the keystone spot. The outfield corners are a possibility as well.

For now, Walker will get a little PT at third while LaRoche rests his achy back. Walker, 24, is no longer a top prospect. However, his position versatility and power make him a good bet to at least have a long career as a super-utility type.

With June right around the corner, we’re going to start seeing more and more top prospects summoned to the big leagues now that their arbitration and free agent years have effectively been pushed back. Soon enough we’ll see guys like Mike Stanton (.456 wOBA at AA), Carlos Santana (.414 wOBA at AAA), and Stephen Strasburg (statistically unmeasurable awesomeness) arrive in the show, but for now we’ve got to rely on some lesser prospects for a fantasy boost.

Here’s two such players that will remain in the lineup for the foreseeable future…

Xavier Paul | Dodgers | OF

With Andre Ethier on the DL, Manny Ramirez dealing with a nagging foot problem, and Garret Anderson’s general ineptitude, Paul has been able to step in and get some regular playing time. He’s started five of the team’s last six games in RF, and in 52 total plate appearances this season he’s put up a .386 wOBA with three steals. Aside from a slight dip in his walk rate (5.8%), Paul’s strikeout (19.6%) and power (.152 ISO) output is right in line with what he’s done in over 700 AAA plate appearances over the last three seasons, though his .326 AVG is propped up by a .405 BABIP.

Even as his balls in play luck starts to go away (.358 BABIP in his minor league career), Paul will provide a decent average and steal enough bases to make him worth a roster spot in an NL-only or deep mixed league.

Juan Miranda | Yankees | 1B

It took 28 team games, but Nick Johnson has finally made his annual trip to the disabled list. He’ll be out until July at the very earliest after having third wrist surgery, but I’ll take the over. Miranda has been summoned from Triple-A purgatory to serve as the lefty half of a DH platoon in Johnson’s stead (Marcus Thames gets the at-bats vs. LHP), and has already managed to whack a pair of homers in a week’s worth of playing time. He’s proved all he can in the minors (.360 wOBA, .194 ISO, 1,500+ PA) and this will be his first extended opportunity in the bigs.

His lefty swing is a good fit for the latest version of Yankee Stadium, and even with some of the regulars playing below their career norms. that lineup offers plenty of RBI opportunities. Joe Girardi has a bit of a fetish with using the DH spot to give his regulars what he calls a “half-day off,” so you’re going to have to pay attention to the lineup each day to make sure Miranda’s actually in there. Like Paul, he’s a decent option in a deep mixed league.

The Tampa Bay Rays have the best record in baseball at 32-13 and not surprisingly are receiving strong pitching performances from all five guys in their rotation. Here are the fantasy numbers for the Rays’ SP:

Those numbers look very good, but let’s examine two other numbers for each pitcher.

The Rays’ staff goes from being excellent to being less impressive after Shields when we look at these other numbers. Davis goes from a very strong #5 pitcher to one who looks more league average. Out of 51 qualified pitchers in the American League, Davis ranks 47th in K/BB and 46th in xFIP. And in his last four starts, Davis has gone 1-3 with a 5.75 ERA. He has 11 BB and 12 Ks in 20.1 IP and has allowed 4 HR in that span.

Normally, the conclusion might be that Davis is just hitting a rough patch and that he should be given a chance to straighten things out. Especially given his status as a former top prospect and a player who is just 24-years old and holding his own in the toughest division in baseball.

But complicating matters for the Rays is the presence of another top prospect in Triple-A who is having great success in Durham. Jeremy Hellickson, rated the Rays’ number-two prospect by our own Marc Hulet prior to the season, is pitching lights-out in the International League this year. Hellickson is 7-2 with a 2.79 ERA in 10 starts this year.

Hellickson has 12 BB and 60 Ks in 58 IP and has allowed just 2 HR. Monday night ne pitched eight scoreless innings against Pawtucket and allowed just one hit. It really is not much of a surprise that Hellickson is doing well in Triple-A. He got a mid-season promotion to Durham last year and went 6-1 with a 2.51 ERA in 9 starts there in 2009.

In parts of two seasons at Triple-A, Hellickson is 13-3 with a 2.65 ERA. He has allowed 27 BB and notched 130 Ks in 115.1 IP. The only less than glowing marker is his ground ball rate. Minor League Splits shows him with a 31.5 GB% (not counting his start against PAW) this season. However, that might be a sample size issue, as he has a 43.5 GB% in his minor league career and had a 44.2 percent mark in Durham last year.

Listed as 6’1 by MiLB, Hellickson does not have intimidating size. Minor league prospect maven John Sickels compared him to Roy Oswalt in this regard prior to this season. Oswalt came up at age 23, spent eight games in the bullpen, moved into the starting rotation in June and ended up with a 14-3 record his rookie year.

It would not be surprising to see Hellickson on a similar path, even if he does not come close to duplicating Oswalt’s W-L record. He has little left to prove in Triple-A and Hellickson has received in-season promotions in both 2008 and 2009. The big question is how long the Rays can remain patient with Davis. A 5.5 game lead in the division makes it easier to allow Davis to go out and pitch every five days without looking over his shoulder.

Still, do not be surprised if Hellickson gets a promotion soon. The Rays waited until September to promote Davis last year, but he did not dominate at Durham like Hellickson. Davis posted a 7.94 K/9 and a 3.40 BB/9 at Durham in 2009. Hellickson’s numbers are 9.31 and 1.86, respectively, this year. Like Oswalt, the Rays could call up Hellickson to begin his major league career in the bullpen with the idea of moving him into the rotation when needed.

Today we’re looking at a couple of deep sleepers for keeper leagues that are intriguing but a little old for the leagues that they’re dominating.

Jerry Sands | 1B | Los Angeles (NL): Sands, 22, got off to a slow start to his pro career with two seasons in short-season ball. Last season, he split the year between short-season and low-A ball. Combined, he produced a triple-slash line of .306/.386/.590 in 288 at-bats but struggled to hit for average in low-A ball. Overall, he slugged 19 homers. Back in low-A to begin 2010, the right-handed hitter is batting .378/.456/.750 in 156 at-bats. He’s slugged 14 homers and driven in 34 batters in 43 games. At 6’4’’ 225 lbs, he’s even swiped eight bags in nine attempts. He’s creaming southpaws with a 1.275 OPS; his career OPS against left-handers is 1.122. Given his age and level of play, you definitely want to be cautiously optimistic over his output. Sands, though, could turn into a pretty intriguing prospect if he can continue to hit for both power and average at upper levels of the system.

Cody Overbeck | 3B | Philadelphia: A 2008 ninth round pick out of the University of Mississippi, the third baseman struggled in ’09 after he was pushed to high-A ball. He hit just .230/.282/.399 in 361 at-bats. His approach was clearly the issue as he posted a walk rate of 5.9 BB% and a strikeout rate of 29.1%. Left back in high-A for 2010, Overbeck has impressed the organization with the improvements that he’s made. He’s currently hitting .329/.393/.621 with 10 homers and 33 RBI in 43 games. Overbeck has been a real run producer for the club and is hitting .400 with runners in scoring position. He’s also made strides in both his walk and strikeout rates. Placido Polanco is not the long-term answer at third base for the big league club, so Overbeck could end up with a key role if he continues to develop.

When the New York Mets opened the 2010 season with top prospect Jenrry Mejia, a 20-year-old righty with scarce experience above A-Ball, in the big league bullpen instead of in a minor league rotation, the move was viewed as a short-sighted play by a GM and manager with tenuous job security.

The Mets have apparently changed course, however. According to ESPN New York’s Adam Rubin, Mejia will return to the minors to get stretched out as a starter. With the oft-pummeled Oliver Perez banished to the ‘pen and Jon Niese at least temporarily sidelined by a hamstring injury (R.A. Dickey to the rescue!), New York is short on starting options and hopes that Baseball America’s #56 preseason prospect can return to take some turns later this summer.

Signed out of the Dominican Republic in 2007 for just $16,500, Mejia split the 2009 campaign between the High-A Florida State League and the Double-A Eastern League. The 6-0, 160 pound (listed) Mejia struck out 7.9 batters, walked 2.9 per nine and had a 61.7 percent ground ball rate in 50.1 FSL frames. In Double-A, he increased his whiff rate (9.5 K/9) and got plenty of grounders (56.3 GB%) in 44.1 innings, though Mejia issued more walks (4.7 BB/9).

Entering 2010, Baseball America described Mejia as possessing 90-96 MPH gas (touching 98 MPH) with “so much cutting and sinking action that it befuddles hitters.” BA also liked his low-to-mid-80’s changeup, while also noting that the off-speed pitch was inconsistent and that his breaking stuff needed plenty of work.

As a reliever in the majors with a praiseworthy fastball and rudimentary secondary stuff, Mejia did what you would expect: he reared back and fired. He used his heater (averaging 94.4 MPH on the radar gun) about 81 percent of the time, supplementing it with a high-70’s curveball (10 percent) and a mid-80’s change (nine percent).

In 17.1 low-leverage innings (0.84 Leverage Index), Mejia had 7.27 K/9, 4.15 BB/9 a 58.5 ground ball rate and a 4.23 expected FIP (xFIP). He had some issues getting ahead in the count, as a sub-50 first pitch strike percentage attests, but Mejia simply holding his own is a testament to his talent.

This is the right move for the Mets–Mejia’s long-term value to the franchise is considerably higher as a potential front-line starter than it is as a reliever. He needs innings to build stamina, hone his control and develop his change and slider.

Similarly, Mejia’s returning to a starting role should be viewed as a positive for fantasy owners. His high K/high ground ball skill set makes him highly coveted in keeper leagues. It’s easier to scrounge for saves that it is to find a premium starting prospect.

On April 23rd, Brennan Boesch stepped into a major league batter’s box for the first time and proceeded to rip the first Rich Harden offering he saw for a double. Since then, the 25-year-old Tigers rookie hasn’t stopped swinging or making loud contact. In just 74 plate appearances, Boesch’s bashing has been worth +7.4 park-adjusted Batting Runs. Where did this guy come from, and what can we expect from him going forward?

Detroit snagged Boesch out of California in the third round of the 2006 draft. A 6-4, 235 pound lefty batter, Boesch fit the physical description of a power hitter but confused scouts with uneven performances for the Golden Bears. Here’s Baseball America’s scouting report leading up to the draft:

He has what scouts look for in a prospect, but while he had set a new career high with 10 home runs, his slugging percentage was actually lower than it was in 2005, and scouts had been disappointed by his overall performance. He’s been erratic, at times showing above-average bat speed and the ability to catch up to good fastballs, and at others showing a long swing that short-circuits his power. His hands are dead at the start of his swing, often keeping him from loading up and generating power.

The Tigers sent Boesch to the short-season New York-Penn that summer, where he hit .291/.344/.435 in 317 plate appearances. He walked in 6.6 percent of his PA and punched out 14.4 percent, posting a .144 Isolated Power.

Boesch ranked 16th on BA’s list of top Tigers prospects prior to the 2007 season, but he dipped to 24th before 2008 and fell off the list entirely leading up to the 2009 campaign. In the Low-A Midwest League in ’07, he batted a weak .267/.297/.378 in 542 PA, drawing ball four 4.2 percent and striking out 15.8 percent. Boesch’s ISO fell to a middle infielder-like .111, with BA saying that he “lacked the plus power expected from a corner outfielder.”

His 2008 season was little better: a .249/.310/.379 triple-slash in 461 PA in the High-A Florida State League, with a 7.8 percent walk rate, a 21.6 percent K rate and a .129 ISO. The MWL and the FSL are difficult offensive environments, but college-trained outfielders hacking and hitting singles aren’t going to elicit much excitement from talent evaluators.

In 2009, Boesch showed an offensive pulse for the first time in pro ball. Bumped up to the Double-A Eastern League, he hit .275/.318/.510 in 571 PA. Boesch remained aggressive (5.8 BB%) and his strikeout rate climbed to 24.1 percent, but his ISO shot up to .235. Baseball America rated Boesch as the 26th-best prospect in Detroit’s system this past offseason.

After a hot start in the Triple-A International League (.379/.455/.621 in 66 PA), Boesch got the big league call and has logged time in the corner outfield and DH spots. He owns a .380/.392/.676 line, with three home runs and a .296 ISO. Boesch’s plate approach, however, leaves much to be desired.

So far, his strike zone has been the size of Lake Michigan. Boesch has chased 50.4 percent of pitches thrown outside of the zone, highest among hitters with at least 70 plate appearances. He’s out-hacking the master of junk ball swinging, Vladimir Guerrero (49.6 O-Swing%). On pitches within the zone, Boesch has taken a cut 84.6 percent. Only Vlad (86.4 Z-Swing%) has swung at in-zone pitches more often. Boesch’s overall 66.4 percent swing rate bests The Impaler’s 65.2 percent mark.

Guerrero might be able to get away with swinging at everything. Boesch isn’t Vlad, though. That 2.7 percent walk rate is going to be an issue once his .421 batting average on balls in play comes back down to Earth.

Coming into 2010, CHONE projected Boesch for a .230/.261/.364 line. That seems pessimistic, but it is important to keep in mind that we’re talking about a mid-twenties prospect with a career .273/.319/.434 minor league line. He has an ultra-aggressive philosophy, and holds a .247/.294/.364 minor league triple-slash against lefty pitching. Boesch isn’t a hot-shot youngster so much as he’s a righty masher with a low OBP and problems with same-handed hurlers.

Mired in a three game losing streak, the Cubs shook things up last week by shifting Ryan Theriot to second base and calling upon top prospect Starlin Castro to assume shortstop duties. Bryan ranked him as the 25th best prospect in the game coming into the season, then introduced you to him on Friday, so let’s not reinvent the wheel and instead focus on what his arrival means for you fantasy owners.

Castro debuted in a huge way, whacking a three run homer in his first big league plate appearance before ripping a bases clearing triple later in the game, making him the first player in history to pick up six RBI in his debut. And that’s on top of being the youngest shortstop in Cubs’ history. It was without a doubt an impressive debut, and as things like that tend to do, it sent more than one owner scrambled to the waiver wire to gobble him up before anyone else did.

CHONE projects a .251/.290/.339 batting line (.280 wOBA by my calculation) with three homers and 14 steals this year, and a projection like that would have him outside of the top 16 fantasy shortstops. Unfortunately for your fantasy team, a big chunk of his value comes from his ability to field a premium position, which does nothing for you unless you’re in a league that counts UZR or +/- (that would be pretty cool).

Even if we want to dream a little bit and say that Castro will instead approach the league average .326 wOBA with 15 or so steals the rest of the year, it puts him on fantasy par with guys like Alexei Ramirez and (not to mix positions, but) Luis Castillo. Basically backup options in mixed leagues or second and third tier starting options in deep mixed or AL/NL-only leagues. However, I look at Castro and think he compares favorably to another NL Central rookie shortstop: Alcides Escobar.

For whatever reason, Escobar has gone from a 20+ SB threat to zero (and just one attempt) through the season’s first month. He says he’s going to steal more, but it hasn’t happened yet. ZiPS sees a .271 AVG with 18 SB and five homers the rest of the way, and I think Castro could give you almost exactly that as well. If anything, I’d expect just a little more pop from the Cubs’ shortstop because of his home park. 20-year-olds are tricky to project, so there’s a whole lotta dreamin’ that has to go on here.

Castro set the bar high in his big league debut, but he’s done a good job of following that up and has reached base in all four games he’s played. If you’re a frustrated Escobar owner, swapping him out with Castro could net you those steals you thought you were getting, and maybe even a little more. He’s owned in just 10% of Yahoo! leagues, so chances are he’s still available in yours as well.

Let’s have a look at a few Deep Keepers.

Bill Rowell | 3B | Baltimore
It’s really never been a question of ability for this former No. 1; his struggles have reportedly been more about attitude and drive. Some times it just takes a little longer for the light bulb to click on for players with questionable makeup. Let’s be cautiously optimistic that this is the case with Rowell. The good news is that he’s still just 21. The bad news is that he’s still in high-A ball, a level he’s been at for three years now. Despite just two homers, he has very good raw power and it’s nice to see him taking some walks and hitting more than .300 – even if it’s with an inflated BABIP.

Matt Davidson | 3B | Arizona
Arizona’s 2009 draft is looking good so far… fingers crossed. With two top prospects in low-A that both play third base (Davidson along with Bobby Borchering), the club has had to get a little creative with playing time so each has seen time at DH, which will hopefully not hinder their development in the field. It definitely hasn’t hurt at the plate for Davidson. The teenager is currently hitting .365/.396/.567 (.479 BABIP) with three homers and 12 doubles in 104 at-bats. He clearly has some work to do at the plate, though, as he’s walked just once all year and has 29 Ks.

Neftali Soto | C/1B/3B | Cincinnati
I’ve been a pretty big Soto fan since ’07 when he was taken in the third round of the draft out of Puerto Rico. He’s had his ups and his downs, but there is hope now that he’s fully ready to realize his potential. Soto has bounced around the diamond a lot, and he continues to do so this season, seeing time four positions, if you count DH. The most exciting development is that he’s seeing time behind the plate (and is actually hitting .500 while playing the position, 9-for-18). Overall offensively, he’s now hitting .306/.343/.500 with five homers in 98 at-bats. He’s repeating high-A ball, but is still just 21.

It probably came a year or two too late, but the Royals have finally called up Kila Ka’aihue, as he takes the place of the injured Rick Ankiel. Better late than never, I guess. The 26-year-old first baseman turned into a bit of a cult hero in recent years, thanks to his ability to completely annihilate minor league pitching while not getting anything more than a cup of coffee in the show.

After posting an ungodly .463 wOBA with 37 homers in 515 plate appearances split between Double and Triple-A in 2008, the Kila Monster dropped down to “just” a .368 wOBA and 17 homers in Triple-A last year. He lost 144 points off his ISO, but his BB% and K% went largely unchanged, as did his batted ball rates according to minorleaguesplits.com. For whatever reason, the power just took a bit of a vacation.

Thankfully, it’s returned this year. Ka’aihue is hitting .304/.466/.620 (.455 wOBA) with seven dingers in 23 Triple-A games (yes, it’s obviously a small sample), and he continues to walk more than he strikes out (230 BB, 169 K dating back to ’08). I’m a sucker for guys that take ball four more often than strike three, but that bias isn’t why I’m recommending Ka’aihue for your fantasy team.

He doesn’t have the big name recognition of say, Ike Davis, but the lefty swinging Royal doesn’t have the massive platoon split either (.821 OPS vs. LHP in the minors, .881 vs. RHP). He might not have the defensive value and long-term outlook of Justin Smoak, but he’s a bit older and his power is more present than projected. Ka’aihue is strictly a 1B, so something’s going to have to give with Billy Butler and Jose Guillen if he’s to get regular playing time. My guess is that Butler stays at first, Guillen goes to the outfield while Ankiel’s injured, and Kila DH’s.

He’s available in basically all Yahoo! leagues (except mine! bwahaha), and if you’re looking for a little boost from the 1B or UTIL spots, here’s your guy. That goes double if you’re in a deep mixed or AL-only league. If you hurry, you should be able to grab him in time for Wednesday’s game.