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.

Here’s two young righties that could be coming to a bullpen near you…

Tanner Scheppers | Rangers

A former second and supplemental first round pick, Texas hasn’t been shy about aggressively promoting the hard-throwing Scheppers since he signed for $1.25M. Baseball America describes him as having “an electric fastball that ranges from 93-99” and a “plus 82-84 mph curveball that could become plus-plus as he refines his command.” The kid clearly has the goods, but after dealing with a stress fracture and what was described as “significant wear and tear” in his throwing shoulder two years ago, it’s possible the team is looking to extract as much value from Scheppers as possible before he breaks down again.

Working strictly in relief, the 23-year-old righty made a strong pro debut in the Arizona Fall League last year, but has just gone off on Double-A hitters this year. In 11 innings he allowed just three hits (one of which was a solo homer) and struck out 19. He’s walked zero, putting his FIP in the sub-1.00 range. The Rangers bumped Scheppers up to Triple-A over the weekend, and a big league relief job is clearly within reach with Texas on top of a winnable division. He might not steal any saves from Neftali Feliz and/or Frank Francisco, at least not at first, but the strikeout and ERA potential should make him worth a spot even in a standard 5×5 league. Once Scheppers reaches the show, he’s a must-get if your league counts holds.

Jake Arrieta | Orioles

The Orioles’ bullpen is in a perpetual state of disarray this days, and there has been some talk of bringing up the 24-year-old Arrieta to help shore things up. While he doesn’t have the same blow-you-away stuff as Scheppers (92-94 mph fastball, slider, change, occasional curve according to Baseball America), Marc projected him as a number three starter down the road. Any move to the bullpen would surely be temporary.

Arrieta has held batters to a .171 batting average in Triple-A, with a 1.93 K/BB and a 2.05 GB/FB in 31 innings this year, good for a FIP just south of 2.00. Because he’s expected to join Brian Matusz and Chris Tillman in their rotation for years to come, there’s no guarantee that Baltimore will promote Arrieta to work in relief, especially when they’re going nowhere fast. If they do though, keep an on him because save opportunities could come his way rather quickly.

With Jason Heyward eating medium leverage situations for breakfast in the big leagues, and Jesus Montero still trying to find his way as a 20-year-old in Triple, the Marlins’ Mike Stanton has grabbed the crown as the “best hitter in the minor leagues” and run away with it. The 20-year-old outfielder smacked three homeruns yesterday afternoon, giving him five within the last 30 hours or so. His ISO stands at .462 this morning, and his walk rate has risen up to match his usually high strikeout rate in the early going. Obviously, small sample size warnings apply.

After a 341 plate appearance cameo with Florida’s Double-A affiliate last year (.344 wOBA), they sent him back there this year, but if he keeps doing what he’s doing now (.495 wOBA by my calculation), it’s won’t be long before they bump him up to Triple-A. Once that happens, it’s only a matter of time before he surfaces with the big league team.

Chris Coghlan has yet to find the BABIP magic he had during his Rookie of the Year campaign last season, and his wOBA sits at just .182. Cameron Maybin is a bit iffy with concussion-like symptoms after colliding with teammate Gaby Sanchez, though he did suit up last night. The Marlins certainly have some need for another outfielder, but whether or not they decide to promote their best prospect will probably end up being a matter of future payroll.

Since the season is already more than two weeks old, Stanton’s free agency has already been pushed back bya year. However, if the Marlins wanted to push back his arbitration years before calling him up, they would have to wait until the end of May, which doesn’t help us fantasy owners any.

If there’s any prospect in the game that could come up and have a Ryan Braun-like impact in the second half as a rookie, it’s Stanton. He might not hit for average right away (or ever), but the power is off the charts (.283 ISO in the minors), and the RBI opportunities will be there with guys like Hanley Ramirez, Dan Uggla, and Sanchez (.399 combined OBP) in the lineup. Stanton is still available in all most leagues, and if you have a particularly deep bench, or are willing to carry a dead spot for a month, then by all means go out and grab him before the rush. Otherwise, keep an Florida’s outfield situation over the next few weeks, and get ready to pounce once they appear to have a need. He’s an option in all leagues.

With the worst wOBA in the American League, the Baltimore Orioles club is looking to kick-start a sluggish offense. As a result, the organization promoted triple-A first baseman Rhyne Hughes to the Majors on Saturday.

Hughes is a name you may not be familiar with. He was not amongst Baltimore’s Top 10 prospects for 2010 when we published the list prior to the season. He did not make Baseball America’s Top 30 list. Hughes was originally acquired from the Rays in ’09 during a late-season trade involving veteran catcher Gregg Zaun. He was drafted by the Rays in the eighth round of the ’04 draft out of a small community college.

The 26-year-old first baseman will make his MLB debut when he is penciled into the lineup for the first time. He was hitting .353/.421/.667 in 51 at-bats this season at triple-A. He had three homers and five doubles in 15 games. Last season with three teams, Hughes hit .279/.349/.506 with 25 homers and 79 RBI in 515 at-bats. He also, unfortunately, had a strikeout rate of 33%.

The left-hand hitting Hughes could platoon with the right-hand hitting Garrett Atkins, who has a .242 wOBA, but is actually performing better against right-handed pitchers right now (He’s 0-for-16 vs LHPs). Hughes has a career OPS of .843 against right-handers (compared to .716 vs LHPs).

From a fantasy perspective, Hughes has little value unless he can wrestle the full-time job away from Atkins. The rookie should be monitored in AL-only leagues but, hey, he’s no Kila Ka’aihue.

From April 16 at FanGraphs: Ka’aihue probably fits best with the O’s. The club is second last in the American League in on-base percentage (.309) and is 11th (out of 14 teams) in slugging percentage. Those just happen to be the two areas that Ka’aihue excels in. He slugged 37 homers between double-A and triple-A in ‘08 and followed that up with 17 at triple-A in ‘09. He’s walked 100+ times in each of the past two seasons and had a walk rate of 18.4% in ‘09. His BB/K rate was an impressive 1.20.

It was inevitable. After just two weeks, the Mets summoned hot shot prospect Ike Davis from the minors to replace Mike Jacobs, the last big power hitting prospect produced by their farm system. Davis had a fantastic big league debut, going 2-for-4 with a run driven in against the Cubbies last night, and the tabloids already have him pegged as the future of the franchise. That’s all well and good, but what does Davis’ arrival mean for fantasy owners?

Supposedly, Davis will play every day at least until the incumbent Daniel Murphy returns, which is good news. There’s no point in calling up your best prospect in April and playing him only sparingly (apparently they haven’t realized that with Jenrry Mejia yet). Davis mashed in the minors, with a .226 ISO and an 11.7 BB% between two levels last year, and he started off this season with a .364/.500/.636 performance in 42 Triple-A plate appearances.

His bane is lefty pitchers, and has been since his days at Arizona State (seriously, who had him beating college teammate and fellow 2008 first rounder Brett Wallace to majors?). Davis hit .267 (.369 BABIP) with a .110 ISO against southpaws in the minors, compared to .297 (.343 BABIP) with a .203 ISO vs. righties, though 191 and 478 at-bats aren’t the largest of sample sizes. He did hang in well to single off Sean Marshall last night, who fed him three curveballs and a slider.

CHONE forecasts a .231 batting average with 11 homers and 39 RBI for Davis in 114 games this year, while PECOTA’s 50th-percentile pegs him for almost the same: .231-11-41. That puts him in Casey Kotchman/Lyle Overbay territory, though Davis certainly offers the potential for more. My hunch is that he’s perform very well his first time through the league, but will start to come back down to earth once the book gets out. At that point he’d be a sell high candidate.

Davis was added to the player pool in Yahoo! leagues this morning, and chances are the Mets’ fan in your league already grabbed him. If not, he’s a worthy add for the bench if your first basemen are underperforming, or if you’re in an NL-only or deep mixed league. Just make sure you sit him against southpaws.

The first few weeks of April are usually pretty quiet for the game’s best prospects, but once May rolls around, teams will begin to call them up after effectively pushing the player’s free agency and arbitration clock back a year. It’s a sound strategy, because usually whatever is sacrificed during those first few weeks of the season (a win? maybe two at most?) is more than recouped in the extra couple of months of team control.

Ryan Braun surfaced in May of 2007 and became not just one of the best hitters in the league, but a savior for many fantasy owners. Evan Longoria did the same in 2008 and last year it was Andrew McCutchen. Finding that one big time prospect who goes from the bush leagues to fantasy megastar is never an easy task, but that’s what we’re here for.

Cleveland’s current catching situation features the tag team of Lou Marson and Mike Redmond, who’ve combined to reach base just four times in 27 plate appearances so far this season. At some point soon the Indians will summon uber-prospect Carlos Santana from Triple-A, who they comically acquired from the Dodgers for Casey Blake and whatever was left on his contract. Our own Marc Hulet ranked him as the seventh best prospect in the game, and the second best catching prospect overall.

In this young season, Santana has gone all Albert Pujols on the Triple-A International League. His triple-slash line sit at .450/.500/1.150, a year after posting a .418 wOBA in Double-A. Six of his nine hits have gone for extra bases (four homers, two doubles), and he’s come around to score seven times in five games. Santana has more walks (181) than strikeouts (170) since 2008, which backs up his reputation as having supreme knowledge of the strike zone. The defensive ability is there as well, so a position switch is not coming anytime soon.

The catching situation in fantasyland is pretty grim beyond the top six or eight players, but Santana could jump right into that mix once he’s promoted. Cleveland has to keep him in the minors roughly two weeks to push free agency back by a year, but about two months to push arbitration back. Count on a mid-to-late May call up.

Santana sports the power, the bat control, and the discipline to be an impact fantasy player once the Indians calls him up, and he’s clearly the best catcher in their organization at the moment. The fact that he plays such a scarce position makes him even more attractive to fantasy owners. If you’re willing to live with a dead spot on your bench for the next month or so, then by all means grab Santana, who’s owned in just 3% of Yahoo! leagues. If not, then make sure you keep an eye on Cleveland’s transactions, because chances are he’ll be an upgrade over your current catching situation or a fantastic piece of trade bait.