Luis Castillo is using his changeup differently

The expectations for Luis Castillo after his marvelous debut season in 2017 were high and understandably so. A good prospect putting up a 3.12 ERA and 3.74 FIP in 17 starts, showing an ability to get strikeouts and ground balls with his upper-90s fastball and elite changeup, makes it hard to temper expectations on him.

Unfortunately, he regressed in his sophomore season. His strikeouts went down, his ground ball-rate took a big hit; and, subsequently, his rate of allow home runs took a large jump. This led to a rather mediocre 4.30 ERA and 4.32 FIP in 169 ²⁄₃ innings. In baseball spectrum, his name was covered a bit of fatigue. Expectations had changed to a wide range for the 2019 season.

But three starts into his 2019 season and his name is back on the radar. Across 19 ²⁄₃ innings, Castillo has struck out 25 hitters, putting up a 0.92 ERA and 1.91 FIP. His ground ball-rate is up, he’s generating more swinging-strikes, and he’s allowing less hard-contact. But not much has changed in terms of his profile. He’s still distributing his fastball, slider, and changeup the same. His velocity has remained stagnant.

Strategically though, there has been some changes. To start out, he’s locating the ball differently three starts in, as among 46 qualified pitchers, not one has a bigger decrease in zone% than Castillo.

Among his 49 career starts, all three of his starts in 2019 rank in the bottom 10 in zone%.

Singling out his signature pitch, his changeup, all the same is happening. The zone% on the pitch is down from 38.3 percent to 28.6 percent. As a results, opposing hitter’s swinging-strike rates have went up from 25.9 percent to 32.1 percent, while their overall production has taken a free-fall from a 56 wRC+ to a -10.

This isn’t the only change Castillo has made with his changeup though. So far, he’s been using it in two-strike counts a lot more, as exactly 50 percent of his two-strike pitches have been changeups, by far the tops in baseball. The usage of his changeup in two-strike counts has steadily increased throughout the past few seasons. In 2017, it was at 29.3 percent, rising up to 40.7 percent in 2018.

Combine the two and you’ll see how much Castillo has completely revamped the strategy with his changeup. In 2017, he ranked 15th out of 141 qualified pitchers in out-of-zone-two-strike changeup%, sitting at 16.9 percent. In 2018, he ranked fifth out of 151, standing at a mark of 26.0 percent. In 2019, he ranks first at 43.7 percent.

Here’s a heatmap of Castillo’s two-strike changeups in 2018.

Here’s 2019.

If this change is more than just noise in a small sample size, than perhaps Luis Castillo could really be onto something here. Learning to utilize his changeup to the fullest extent and pairing it with a hard fastball could make significant waves for him and the Reds.

Patrick Brennan loves to research pitchers and minor leaguers with data. You can find additional work of his at Royals Review and Royals Farm Report. You can also find him on Twitter @paintingcorner.