Why is Miguel Castro suddenly so effective?

How the Mets' reliever is finding success this season.

Miguel Castro is sort of like that deep track on your favorite album that everyone knows and likes, but for some reason is never played on the radio or listed as a top song.

Granted, after arriving in New York from Baltimore last season, the right-hander lost his command and finished the season with a 4.01 ERA, but armed with a 98 MPH sinker, a swing-and-miss slider, along with a change-up, the stuff was like a catchy beat behind lackluster lyrics, which I suppose explains why we have to compare him to a deep track instead of a hit song.

But after spending the offseason tinkering with his repertoire, Castro is starting to play a sweet tune out of the Mets’ bullpen. He’s only made seven appearances, but the changes he has made to his pitch mix offer reason to believe his impressive strikeout-to-walk ratio isn’t just a product of a small sample size.

Castro can throw the ball hard. That is obvious. His sinker that nearly touches 100 MPH is one of the heaviest in baseball, and he hasn’t done much to change his go-to offering over the past year. What he has done is improved his secondary pitches. 

By manipulating the spin characteristics on his slider and change-up, he has drastically changed the shape of both pitches, creating greater separation from his fastball, and thus, giving himself a platoon-proof arsenal to use against either lefties or righties during a time when the rules of baseball have forced managers to trust relievers against opposite-handed hitters.

Castro’s slider and change-up have each added 3+ inches of drop since last season, and his slider has doubled its sweeping action from right to left. As a result, he’s getting a 50% whiff rate on his slider (mostly to righties) and a 47% whiff rate on his change-up (mostly to lefties). His arm angle has always produced above-average side-to-side movement, but by fostering more depth on each of these offerings, they have both become lethal offsets to his fastball, particularly his change-up, which hasn’t always been the case.

You can see in the video below how the righty is able to find success using his change-up off his sinker by messing with the hitter’s timing (with a 6 MPH velocity gap) and generating that sharp added movement.

How is he doing this? I will save the detailed lecture on “seam-shifted wake” for another post, but for the purposes of this newsletter, it’s important to know there is new research that suggests there is a force other than the Magnus Effect that contributes to the movement of pitches as they approach home plate. 

This is called seam-shifted wake and found most prevalent in sinkers and change-ups. And it explains why pitches move in seemingly unpredictable ways, such as when we look at the spin direction of Castro’s change-up as measured by Hawk-Eye (left image below) relative to what we would expect the spin direction to be based on the actual movement of the pitch (right image).

IN SHORT: Castro throws his sinker and change-up from similar release points with very similar tilt (think of the baseball tilted toward 2:00 on a clock), which would suggest they should move similarly, other than the impact imparted by gravity due to their different spin rates and velocities. However, his change-up moves with significant more horizontal movement than expected, which, as we showed in the video above, creates deception when sequenced with his sinker, and it aligns to the research of how seam-shifted wake impacts this pitch type.

By throwing his change-up a little slower (well, slower for Castro) and with less spin than he did last year, he is gaining more drop, along with strong arm-side movement from what appears to be non-Magnus effects. He adjusted his slider a bit differently, altering his grip and/or release to reduce the amount of gyro (and thus reducing seam-shifted wake effects) in exchange for spiked movement. Together these changes have made both pitches even more distinct from his sinker in both velocity and shape.

BOTTOM LINE: Miguel Castro’s early success isn’t just the result of making a few good pitches here and there. He has improved his secondary pitches to make himself a much more dangerous option out of the bullpen.