Some say the sample size of Luis Castillo’s season is 15 starts; I say it’s only eight.

July 25th was the first game in which BrooksBaseball.net registered a Sinker from 24-year-old. While some other sites show blips of the pitch peering out from behind the curtain – misread changeups? – you’ll read elsewhere that he learned the pitch right as the August sun crept up on the city of Cincinnati. After adopting the sinker, his following eight starts showed a clearer picture of the pitcher he’ll be in 2018.

The issue the resonated most with analysts during his debut at the end of June was his fastball’s tendency to stay straight. An old adage you’ll hear in baseball circles revolves around a straight fastball’s velocity mattering less, because if it’s a straight 98-99mph pitch, theoretically, a major league hitter will have a better chance of squaring it up.

Castillo never got that memo.

Unless the Yankees’ ace Luis Severino concentrates some adrenaline to kick up his average fastball velocity by season’s end, Castillo will claim the “velo crown” for starting pitchers – 97.8mph is number (min. 200 pitches). While velocity doesn’t tell the whole story – I’m looking at you 2016 Nathan Eovaldi and your 97.8mph average four-seamer – for Castillo it’s a catchy interlude; a hook that gets your undivided attention. Even with the pitch and its “straight” tendencies, aggregating all 15 of his starts, the pitch maintained a whiff-per-swing rate inside the 85th percentile among all starters – 22.6% (min. 200 pitches).

It may seem dubious that the hardest fastball among starters in all of baseball could get better during any stretch of time, but Castillo wove into his repertoire a sinker that allowed his four-seamer to change its attack.

Above we’re looking at Castillo’s four-seam fastball location pre sinker adoption (before July 24th) and post sinker adoption (July 25th forward). The former being a tight concentration towards the outside part of the plate, while the latter is the much larger area of dark red, up in the zone.

This philosophy makes sense; take a straight fastball, stop throwing it for strikes down in the zone, and put it at the letters, making it nearly impossible for hitters to muster success. It worked. Castillo wasn’t able to execute this move sooner because he didn’t have another fastball to establish the zone with early in starts.

Before Castillo’s sinker, hitters were teeing off on Castillo’s fastball to the tune of a .658 slugging percentage. All the while, his slider and changeup – which we’ll touch upon shortly – were nearly unhittable with slugging percentages that couldn’t edge past the fabled “Mendoza Line.” After Castillo learned his sinker, that cringe-worthy slugging percentage on his four-seamer fell to manageable .368.  His sinker, meanwhile, was his early-count pitch, and he located it unbelievably well. Castillo’s worm-killer was second among starters with a 77% grounder-per-ball-in-play rate, trailing only Jordan Zimmermann, who can’t sniff the whiff rates of our Dominican-born phenom (almost as good as Carrasco’s sinker). As Eno Sarris mentions in a Fangraphs’ column, Castillo is creating a duo of skills that most pitchers envy: choppers and whiffs.

Those whiffs come from his slider and changeup, two pitches that stood out before the sinker, becoming much easier to “arrive at” in terms of sequencing with a two-percent cut in walks and improved ability to get ahead of hitters. His changeup – like most righties – is a put-away pitch to left-handers; 33% usage rate overall that kicked up to 43% when Castillo had two strikes on a lefty. The sinker we’ve discussed at length also seems to correlate with an uptick in slider usage to left-handed hitters. It ticks up 8% when Castillo has two strikes on a hitter. My speculation is this has a bit to do with gaining confidence in the pitch through understanding eye-level adjustments that hitters have to make after realizing Castillo is now living up in the zone with his four-seamer (see the GIF above). Of course, this is merely speculation; it could easily be Castillo becoming more comfortable with the break of the pitch, eliminating fears that he doesn’t follow-through and leave it up in the zone – essentially a meatball.

Sitting just below Castillo’s changeup in terms of velocity is his preferred put-away pitch to right-handers, a compact slider that doesn’t jump out in terms of swinging strike rate, velocity, or even movement, but possesses an uncanny ability to avoid becoming line drives. A peculiar metric to stand out in, yes, but after understanding line drives go for hits three times more often than ground balls, limiting line drives becomes the best thing you can do if you’re offering a pitch void of Kershaw-territory whiff rates.

A 27% strikeout rate in just under 90 innings, with a groundball rate near 59% is a combination very few pitchers possess; Castillo is one of them. With his sinker in play, those numbers became 25% and 61% respectively, just as dominant, yet more stable with the improved control I’d speculate the sinker brought about. I’ve heard a lot of Luis Severino and Michael Fulmer comparisons to Castillo because of the fastball-slider-changeup offerings, but one of the best young pitchers in baseball is becoming a unique beast with his sinker.

Castillo’s potential is the good kind of unbelievable, in contrast to another kind of unbelievable from this Cincinnati.com article titled, “Bryan Price: Luis Castillo is in the 2018 Rotation” which implies we needed to know one of the best young pitchers in all of baseball will be allowed to dominate as a starter come March 29th of 2018. March? Yes, March. Baseball and snow is quite possibly my second favorite pairing. Behind, of course, the whiffs and grounders Castillo generates.

Lance

Photo via the Flickr Creative Commons, thanks to AP3 for the shot of Luis Castillo.

Statistics all from Fangraphs, BrooksBaseball.net, and Baseball Prospectus unless otherwise noted.

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