Analyzing Three New Rookie Starting Hitters — A Review

In early April, I discussed three less heralded prospects that entered the season with starting jobs and used bulleted lists to share what I liked and didn’t like about each rookie. Let’s now review my likes and dislikes versus what actually transpired. Below each of my original bullet points will be an update in italics describing what ended up happening that relates to that bullet point.

Jeremy Peña | HOU SS | #31 overall prospect

What I Like

• Massive power spike at Triple-A in 2021 (.311 ISO), driven by 37% HR/FB rate

He held half his power spike, as his HR/FB rate remained significantly above his pre-2021 breakout level, but still less than half his 2021 mark at Triple-A. His ISO finished in a similar boat, but was less impressive and closer to his pre-2021 marks.

• Owns above average speed too and willingness to use it, with a 600 PA pace of 22.5 steals in 2021

He swiped 11 bases in 13 attempts, a good success rate, but didn’t run as often as he did in the minors. Of course, that’s not surprising considering he posted just a .289 OBP, which reduced his opportunities.

• The Astros failing to sign either Carlos Correa or Trevor Story suggests their confidence in Peña

He held a starting job all season long and recorded 558 PAs. They liked him so much, he batted second more often than any other spot, despite the weak OBP.

• He grades out as a plus defender, which should give him more of an opportunity to overcome a slow start at the plate or a mid-season slump

He won the AL Gold Glove, was tied for the highest DRS (defensive runs saved) among shortstops in baseball, tied for 9th in OAA (outs above average) and ranked 8th in Def rating. However, he posted a -9.6 UZR/150, which is quite bad. It’s hard for me to understand how he was so strong in the other metrics, but so poor in UZR!

What I Don’t Like

• That Triple-A power spike came over a tiny sample of just 122 at-bats

Aaaaaand, he couldn’t maintain it, but it was such a massive spike, we couldn’t have expected anyone really to maintain it. Maintaining half that HR/FB rate spike was still plenty good enough.

• SwStk% has risen at each subsequent minor league level, driving up his strikeout rate to a professional worst at Triple-A

His SwStk% stabilized and finished similarly to his Triple-A mark, while his strikeout rate actually improved marginally. Swinging at everything helped keep his strikeout rate at bay, despite all the whiffs.

• He has stopped taking a walk, as his walk rate has been in freefall since Single-A in 2019

His walk rate fell to just 3.9%, leading to an ugly .289 OBP. The Astros didn’t care that he couldn’t get on base though given how often he batted second!

• His FB% plummeted at Triple-A, reducing the benefit of an insane 37% HR/FB rate

His FB% barely increased off his Triple-A low, potentially knocking a couple of homers off his total, but perhaps raising his BABIP.

• Even with more grounders and fewer fly balls, his BABIP fell at Triple-A to the lowest mark since his 2018 debut in Low-A

His BABIP fell even further to just below .300, which still represented a slightly above league average mark.

Diego Castillo | PIT 2B/SS | #17 Pirates prospect

What I Like

• Those SwStk% marks! Since 2017, he hasn’t posted a mark exceeding 7.2%, so he could really make contact, driving a strikeout rate between excellent and elite levels

Whoops! His contact ability really took a dive during his time at Triple-A and during his MLB debut this year. His SwStk% jumped into double digits for the first time, while his strikeout rate jumped above 20% for the first time.

• Increasing walk rate and right around league averages, despite such strong contact ability. Often times you see low walk and strikeout rates as a hitter makes such good contact, he doesn’t even get a chance to take a walk and see four balls before putting the ball into play.

So much for the increasing walk rate! He stopped walking while with the Pirates, and actually posted a professional low mark.

• He transformed into a fly ball hitter in 2019 and has maintained that fly ball tendency since

His fly ball tendency continued in the Majors, as he posted a 40.3% FB%. That allowed him to make the most of his mid-teen HR/FB rate.

• His power surged in 2021, as his HR/FB rate went from the low single digits to double digits, while his ISO spiked from sub-.100 to at least .164

The power translated, as he posted a 14.3% HR/FB rate and a .176 ISO. While far from elite, it’s a significant step up from his 2015-2019 years, when he failed to post even a 3% HR/FB rate and only exceeded a .100 ISO once. It confirms that his 2021 power breakout was real.

• He owns some speed, swiping about 12 bases over a 600 PA pace in 2021

He stopped running. He only attempted two steals, succeeding once. Sure, his OBP was an ugly .251, but he definitely ran less often when he did have the opportunity. It’s always difficult to predict how often players with just average Sprint Speed and HP to 1B times will run in the Majors.

What I Don’t Like

• He has run low BABIP marks over nearly the entirety of his minor league career, which will offset much of the benefits of a low strikeout rate on his batting average and OBP

Yup. He posted just a .239 BABIP, which combined with the disappointing mid-20% strikeout rate, resulted in just a .206 average.

• He’s on the Pirates, the team we project to score the second fewest runs scored in baseball, which will limit Castillo’s runs scored and RBI totals

The Pirates outperformed! Rather than finishing second to last in the Majors in runs scored, they finished fourth to last! Castillo ended up with just 57 RBI + R, or about 114 over a full season. That’s not good.

• He figures to open the season batting eighth in the lineup, which isn’t ideal in any lineup, let alone the second worst lineup in baseball

He actually ended up batting fifth most often of any lineup slots, but that didn’t really matter on a bad offense while posting a .272 wOBA.

• He’ll have to perform at least somewhat decently, as the Pirates are loaded with middle infield options, plus Oneil Cruz in the minors

He was demoted to the minors at the beginning of August and didn’t return until mid-September, with Cruz taking over the starting shortstop job.

Kevin Smith | OAK 3B | #23 Athletics prospect

What I Like

• A history of above average power in the minors, plus his highest HR/FB rate during his first year at Triple-A in 2021

His power went bye bye. It was a small sample, as his struggles resulted in a demotion, but his HR/FB rate slid to just 4.4%, while his ISO settled at just .122. I expected more.

• A surging walk rate that jumped into double digits for the first time at Triple-A in 2021

Welp, that was a fluke! His walk rate finished at a professional low at 4.6% with the Athletics, and dipped back into single digits during his time at Triple-A.

• A rebound in strikeout rate and SwStk% in 2021 after both increased dramatically at Double-A in 2019

Both metrics increased after their 2021 Triple-A rebounds, and got even worse during his time in the minors.

• A fly ball tendency that makes the most of his home run power

He maintained that high FB%, but it barely mattered given how few of those flies left the yard.

• Speed and a willingness to use it – a 26 steal pace over 600 PAs using his 2021 Triple-A rate

He stole 4 bases, without getting caught, for a 16 steal pace over a full season. He even managed to do that while posting a .216 OBP!

• Given the obvious rebuilding efforts, Smith’s leash should be long, especially with few decent alternatives at either third base or shortstop

Even rebuilding teams have a limit to how much weak offense they could stomach. Perhaps on a contending team, Smith wouldn’t have even lasted 151 PAs of a .226 wOBA before getting the boot.

What I Don’t Like

• Lots of fly balls and a potentially high IFFB% could result in a low BABIP

That’s what happened! He kept hitting those flies and lots of pop-ups, leading to a .237 BABIP. With a worse than average strikeout rate, that’s how you hit below the Mendoza Line.

• He’s on the Athletics, the team we project for the fewest runs scored in baseball, which will limit Smith’s runs scored and RBI totals

The Athletics finished second worst in baseball in runs scored, with just nine more runs than the last place team, the Tigers. Smith only totaled 22 RBI + R, for a pace of 88 over a full season, which is sad. Even if he actually hit well, that total would probably still have ended up unimpressive.

• He figures to open the season batting eighth in the lineup, which isn’t ideal in any lineup, let alone the worst lineup in baseball

He did indeed hit eighth more often than any other spot and certainly didn’t hit enough to convince the team to move him up in the lineup.

Currently, my favorite is Jeremy Peña , simply because his playing time appears more secure at the moment and I’m willing to gamble on some of that massive power breakout being real. Also, he’s part of the best lineup by far, which will have a significant impact on plate appearances, runs scored, and RBI totals.

In hindsight, this looked like the obvious choice of the three, but all of them had enough good points to seemingly have upside. Pena was the only one of the trio that delivered any sort of positive value, and he likely ended up earning his owners a nice profit.