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  • Justin Dunbar

Dissecting Luis Castillo

Heading into the 2021 MLB season a major storyline for fantasy baseball was how to go after pitchers in the draft. With innings likely to be more spread out than normal there was a greater value placed on frontline starting pitchers who wouldn't be limited from an innings perspective. Targeting one of those players early would greatly increase the floor of your pitching staff.


Gerrit Cole, Jacob deGrom, and Shane Bieber established themselves from the pack but outside of that the cluster of pitchers selected after them were extremely interchangeable. One pitcher who many held in high regard was Reds' ace Luis Castillo. Drafted as the 10th pitcher, according to Fantasy Pros, the 28-year-old was seen as an ascending ace and was expected to help anchor fantasy owners' respective pitching staffs.


The reason for this faith made a lot of sense. Castillo was coming off of an impressive 2020 season in which he struck out 30.5% of the batters he faced, decreased his walk rate to a more modest 8.2%, and actually posted a lower FIP (2.65) than Cy Young winner Trevor Bauer. Yes, it was a shortened season yet this appeared to be a continuation of development after a 4.1 fWAR season in 2019. Although progression isn't linear, it looked to be the case for him, and some even thought he'd be in contention for an NL Cy Young award this year.


Naturally, Castillo's first month to the season has been as unexpected as possible. Over his first six starts, he has posted a 6.07 ERA, has seen his strikeout rate (17.9%) be almost cut in half, and doesn't rank in the top 100 in fantasy points for starting pitchers. Now the question isn't whether Castillo can be your ace, but someone you can rely on at all. Fret not fantasy owners! Together we'll be able to figure out what has gone wrong with Castillo and if he can turn his season around!


Immediately, what stands out with Castillo is that he's not striking batters out which correlates with his 10.9% swinging-strike rate, down from 15.4% in 2020. His fastball and sinker are getting hit hard (-7.6 runs above average) and he's allowing an 8% barrel rate. Problem solved; we have identified the problem!


Of course, however, it cannot be that simple. Castillo is striking out fewer hitters and is getting hit harder yet he's also:

  • Inducing the highest chase rate (35%) of his career

  • Is throwing his elite changeup (39%) more than ever

  • Hitters are swinging less on pitches in the zone, and he's inducing for called strikes (16.6%)

  • He's gotten more first-pitch strikes (63.4%)

So hitters are swinging at more unfavorable pitches and despite throwing in the zone less often (46.2%) he's getting more called strikes than ever. That seems to be good, right? There are a lot of inconsistencies present here and over time I'd expect his walk rate to spike and for his called strike rate to go back down. Nevertheless, if hitters are expanding the zone more and he's throwing his best pitch more often why has his effectiveness decreased so much?


Could it be command-related? Well his meatball% (6.5%) hasn't changed from last year and hitters are swinging at those pitches less (73.5%); in fact, he is throwing more pitches on the edges than ever (46.9%). Now, that doesn't exactly tell the whole story as he hasn't done as sound of a job locating his fastball and sinker in an east/west location ideal (sinkers into righties, fastballs away), but it's not as though his command has been egregious.


Is it related to his arsenal? Well, his movement per pitch types are extremely similar to what they have been in the past and his fastball velocity is in the same range as what it was in 2019. Remember his pitch mix appears to be more optimized than ever and the chase rate is a very encouraging sign.


So, what is the problem? Really, could there be no problem? Here's Castillo's out-of-zone contact rate by year:

  • 2017: 55.8%

  • 2018: 59.6%

  • 2019: 50%

  • 2020: 52.9%

  • 2021: 70.3%

That seems like an outlier to say the least. A key principle in statistical analysis is that over time, statistics will regress back to mean, and along with his batted-ball data, which is more unreliable for pitchers than hitters, that's likely to be the case for Castillo. The idea that hitters have suddenly become so acclimated to hitting his pitches outside the zone seems like a stretch.


Adding more validity to this, Castillo has had two games when he has posted a swinging strike rate below 10%. What is so fascinating about this? Well, they both came against the Cardinals who have the fourth-highest contact rate in the MLB and made contact on 90% of the pitches he threw outside the zone in his first game. Plus, outside of one start against Pittsburgh, his five other starts came against top-18 offenses and his schedule over the next month is much more favorable:

  • CLE

  • COL

  • SF

  • MIL

Although Castillo struggled against San Francisco in his first outing it was also his best game from a strikeout perspective and the Brewers have had issues making contact and scoring runs all season. To top it off, Cleveland is a great bounce-back opportunity for him, and although Coors Field is always scary, the Rockies' lack of offensive productiveness helps ease those concerns.


In my opinion, there is no benefit from selling low on Luis Castillo. You can be worried about the ballpark and the infield defense, especially since they are shifting far less versus lefties (.431 BABIP), but this is a classic case of regression to the mean. His process is very sound and over time the results should show. Honestly, given the division he is in, his schedule is going to be in his favor. There will be plenty of chances for him to get back on track. Really, though, he doesn't necessarily need to get better. Rather, the results just have to be consistent with the results. When you're inducing more chases than ever and throwing your better pitches more I'm assuming you're going to eventually find success. If you can find someone ready to sell Castillo that is something you should immediately look into. We talk a lot about statistical terms but it's really exciting to see it actually play out in real-time and that is something I hope to do with Cincinnati's ace.