Last week, we began to delve into how Luis Castillo can become the ace the Cincinnati Reds are searching for. We looked specifically at his velocity, fastball command, and arm angle. Those are just a few critical components of a pitcher’s game, however. Pitch selection and sequencing are equally, if not more, important.

There’s little doubt he possesses one of the best changeups in the game. His mid-to-upper-90s fastball gives him two weapons to unleash against hitters. His other two pitches — a two-seamer and slider — aren’t quite as effective, though for different reasons.

Two-Seam Fastball

Castillo developed a two-seamer — or a sinker, depending on the pitch tracking system you’re using — in the middle of his rookie season. Its movement is impressive. The pitch has significant arm-side ride, darting away from lefties and toward righties. Aesthetically, it’s an impressive offering.

Despite that impressive movement at 96, it’s the weakest weapon in his arsenal. None of his pitches have a lower swinging-strike rate (5.7%) or a higher contact rate (88.5%). A sinker isn’t designed to miss bats, which is part of the problem. At its best, the sinker will, of course, get a lot of grounders. That was the case in 2017 for Castillo; he generated ground balls three-quarters of the time his sinker was put into play. Last year, however, showed the problem with a sinker. Because it doesn’t get whiffs, variance in luck can lead to more base hits and poor command can lead to more elevated (and hard) contact.

Castillo’s batted-ball luck with the sinker, despite falling to a 57% ground-ball rate, improved. It registered a .295 batting average when put into play in 2017 and a .271 BABIP last year. Erratic command, though, yielded worse results. The slugging percentage for batters when putting it into play rose from .420 to .487. The isolated power increased from .140 to .192. The exit velocity rose from an average of 87.7 to 90.5 mph. He allowed eight of his 28 home runs on the two-seamer, the second most of any pitch behind the four-seamer.

These problems — like his problems as a whole — depended on which side of the plate the batter stood. Castillo’s sinker held righties to a .218 average (.260 xAVG), .321 slugging percentage (.387 xSLG), .245 weighted on-base average (.291 xwOBA), and an 87.7 mph average exit velocity. Its swinging-strike rate against righties (10.2%) was far higher than the league average (6.7%), and he still got an elite ground-ball rate with the pitch (63.4%).

Against lefties, the pitch did not fare well. At all. They managed a .394 AVG (.359 xAVG), .704 SLG (.673 xSLG), .495 wOBA (.470 xwOBA), and 93.4 mph average exit velocity. All of those marks were the worst of any pitch. Despite the sinker’s ineffectiveness, he still threw it 20% of the time against lefties.

The answer to why it was ineffective is pretty simple and something we’ve already touched on: command. Take a look at where he located the pitch in 2017 compared to 2018 (keep in mind that this view is from the pitcher’s mound, just the way you’d see it on TV):

You can see a lot of misses over the heart of the plate and on the outside corner. The latter location is ideal for right-handed hitters because a sinker will tail toward them and away from the barrel of the bat. Against lefties, it’s bad news. Whether he was afraid of hitting the batter or simply didn’t trust the relatively new offering, Castillo rarely challenged hitters inside with a front-door sinker. Leaving the pitch in the middle of the plate rather than down also played a significant role in the sinker’s decrease in grounders and weak contact.

Here’s a look at a heat map of the sinker’s exit velocity by zone against lefties (this graphic is from the catcher’s point of view):

The results aren’t surprising. The sinker got mashed when he missed in the middle of the zone and didn’t get a single ball put into play on the inside part of the plate because he couldn’t locate the pitch there. Castillo found success when he threw the pitch low and away from left-handers; it’s where he got most of his ground balls against them. He just didn’t do it regularly enough.

What should Castillo do with the sinker, then? Should he scrap it? If he can’t command it better, he’d certainly be better off significantly cutting down its usage against lefties. In general, though, sinkers and two-seamers are not highly effective pitches in today’s game. Hitters have embraced launch angle and are better at driving balls low in the zone where sinkers live. Elevating them isn’t particularly effective, either, because they generally have a low spin rate compared to a four-seam fastball. Spin rate is highly correlated with whiffs for four-seamers because the pitch falls slower with when it has more revolutions per minute. Batters expect the ball to drop and it doesn’t, leaving them to swing underneath it.

As a result, the league has started to shy away from using sinkers over the last decade. In 2008, 23.5% of all pitches were two-seamers/sinkers. That number was down to 19.8% in 2018. The league is throwing fewer fastballs as pitchers embrace off-speed and breaking pitches more, but the sinker/two-seamer is taking the biggest hit as missing bats becomes a higher priority. Some pitchers are still effective sinker-ballers, but they’re a rare breed.

All that is to say Castillo should probably rely on it less moving forward. On Opening Day, Castillo did not use a sinker at all. Whether that trend continues will be interesting to watch.


Movement and velocity are eye-catchers, but we can’t overlook when a pitcher throws their pitches. To get out lefties, in particular, Castillo would benefit tremendously from a breaking pitch that rides on a different horizontal plane. The four-seamer, sinker, and changeup all tail away from left-handers. Fortunately, he already has a pitch in his arsenal that moves a different direction: the slider.

While he throws it plenty against right-handers — over 20% of the time in his career — he’s reluctant to throw it against left-handers (5%). He didn’t seem to have a feel for it last year, struggling to bury it down and in consistently against lefties and mostly shying away from it.

Because Castillo doesn’t trust his slider against left-handed hitters, lapses in command have worse consequences. His other three pitches all ride away from lefties. If he tries to locate the pitches inside and misses, that means they tail right over the middle of the plate. The slider, on the other hand, moves toward the hitter. Batters are much less likely to do damage on pitches inside, and ones with different movement keeps them guessing. As a result, the pitcher can get weaker contact and whiffs. If Castillo can master his command of the slider, he can also throw a backdoor slider to lefties, something he did to strike out Corey Dickerson on Opening Day.

On paper, Castillo’s slider is a fairly average pitch right now. It has a solid — though not elite — swinging strike rate of 16.1% in his career (vs. league average of 17.0% in that time) and a below-average chase rate (23.3% vs. 32.1% league average). The pitch has decent movement, but Castillo sacrificed some ride and velocity for drop last year. It resulted in more swings and misses but fewer grounders and a worse outcome when the ball was put in play. That said, it still held hitters to a .641 OPS and .277 wOBA.

Notably, though, he started to decrease the slider’s vertical movement as the season moved on in favor of more velocity, a positive step back toward his 2017 form when the pitch held batters to an .093/.111/.116 slash line.

Still, his usage of the slider against left-handers didn’t increase even as he pitched better down the stretch. How did Castillo’s lack of feel for the slider affect his performance against left-handers in 2018? As discussed in last week’s column, it made him more predictable, even with his devastating changeup (this is discussing arm angle, but low slider usage also plays a role in these numbers):

“In pitcher’s counts when [hitters] can’t sit on a fastball, they can reasonably guess a changeup is coming and confirm that by watching Castillo’s arm angle. Lefties had a 24.8% whiff rate against his changeup in 2018 — still excellent but quite a difference from the 30.6% mark he had against right-handers. As further evidence, left-handers made contact on his changeup on 39.1% of their swings versus just 19.8% for righties.”

This was also evident with two strikes when Castillo needed a putaway pitch. He mixed his pitches well against right-handers with two strikes: 30.9% four-seamers, 34.8% changeups, and 22.4% sliders. That gave him three options with different speeds and movements to put a hitter away. His strikeout rate was 24.9% against them, and they slugged just .206 with a .219 xwOBA in two-strike counts.

That variety didn’t exist against lefties.  The changeup was still his go-to, but he relied on it too much (46.4%). His four-seamer (36.4%) was the only other pitch he threw more than 10% of the time with two strikes. He threw a slider to lefties in two-strike counts only 7.0% of the time. Thus, he lost some unpredictability. His strikeout rate was 21.7%, and batters slugged .381 with a .277 xwOBA. The league average slugging percentage for a left-handed hitter against a right-handed hitter in these situations last year was .288 with a .243 xwOBA.

Castillo worked on his slider over the offseason, and coaches have encouraged him to revisit his curveball — a pitch he hasn’t thrown in the major leagues. If he’s committed to scrapping the sinker, he’ll certainly need to rely on the slider more this season. The question is whether he’ll do so against lefties or whether a fastball-changeup combination is enough to get by as long as he continues to dominate righties. If the command is better, it might be. But it wouldn’t hurt him to have another weapon in his arsenal to finish off hitters.

All stats and graphics courtesy of FanGraphs, Brooks Baseball, and Baseball Savant.

2 Responses

  1. Jordan Barhorst

    Great series, Matt. I think we can all agree Castillo definitely has the potential to be a bonafide Ace for this team. Opening Day was encouraging – I’m excited see how he pitches today.

    • Matt Wilkes

      Thanks, Jordan! I’m optimistic the new pitching coaches will help Castillo put it all together.