Luis Castillo and His Fastball Heat Up as the Trade Deadline Approaches

With the All-Star break in the rear-view mirror, the eyes of the baseball world turn to the upcoming trade deadline, which is now less than two weeks away. Juan Soto’s sudden availability is dominating the headlines, pushing the rest of the field to the back burner with the focus on the possible blockbuster deal. Still, for the majority of teams who are priced out of the Soto sweepstakes, there’s no shortage of interesting trade candidates to go after over the next few weeks.

For teams looking for pitching help, the top option on the market is almost certainly Luis Castillo. A pair of shoulder injuries to the two other top targets has thrown a wrench into the market; Frankie Montas threw three innings yesterday in his first start since July 3, and Tyler Mahle is scheduled to make his first start off the IL on Sunday. It’s certainly possible either Montas or Mahle (or both) will be dealt in the next few weeks, but teams will understandably be more cautious with them.

Castillo dealt with his own shoulder injury this spring which held him back from making his season debut until May. He wasn’t all that sharp through his first four starts, but he’s turned it on since then, averaging more than six innings per start since and allowing just three total runs across his last four turns. During this recent hot streak, he’s struck out 33 batters (a 30.8% strikeout rate) in 27 innings. In his final start before the midseason break, Castillo held the Yankees to a single run in seven innings, allowing two hits and four walks and striking out eight.

Well known for his fantastic changeup, that pitch hasn’t been nearly as effective as it has been in the past. Over the first five seasons of his career, he ran a 41.2% whiff rate with the pitch, the fifth-highest whiff mark for a changeup during that period. This year, that has fallen to just 25.1%, a career low and the third year in a row it’s dropped. It’s still an effective pitch at limiting hard contact (.305 xwOBAcon), but batters simply aren’t swinging and missing at it as much as they used to.

To combat the slow decline of his changeup, Castillo has turned to his four-seam fastball, throwing his heater more often than his cambio for the first time since 2018:

It’s still a bit of a surprise to see him turn away from his changeup despite its lackluster results this year. That pitch has been such a dominant weapon for him, and he’s relied on it as his primary out pitch for the last three seasons. The biggest reason why he’s turned away from it, though, isn’t because of its loss of effectiveness; it’s because his four-seamer has been better than ever before.

Prior to this year, Castillo ran a 26.2% whiff rate on his fastball — a bit above average for that pitch type, but not outstanding. This season, the whiff rate on the pitch is approaching 40%; among all four-seam fastballs thrown at least 100 times in 2022, that’s the best in baseball.

The key to the big heater improvement stems from the amount of ride he’s able to generate with the pitch, as he’s added more than an inch of carry while maintaining the same hard velocity he’s always had throughout his career. The spin rate on his fastball also spiked by nearly 150 rpms last season, and it’s even higher this year. And while he wasn’t able to translate that extra spin to additional movement in 2021, it’s finally taken hold in ’22. That additional ride he’s been able to generate with the pitch has unlocked the benefits of another adjustment he also made last year, when he dropped his vertical release point by almost a quarter of an inch; he’s maintained that same lower release this season.

When we talk about ride and release points in combination, we’re really talking about flat fastballs. Four-seamers with flat vertical approach angles (VAA) are extremely effective, particularly up in the zone. VAA is a function of a pitch’s velocity, release height, and location; those three interrelated factors help us understand why an extreme VAA would help a pitch outperform its raw physical characteristics. For Castillo, the adjustments he’s made to the shape of his fastball and his release point have turned his fastball into a monster:

Castillo has consistently increased his VAA from above-average to elite over the last two years. He had already been locating his fastball up in the zone regularly, but lowering his release point last year helped him make the first jump, and the extra carry on the pitch got him all the way there.

The benefits can be directly seen in the phenomenal whiff rate the pitch is generating, but they extend beyond that one metric:

Castillo is running the highest zone rate of his career, and opposing batters are swinging at his fastball more than ever before as a result. They simply can’t make solid contact with the pitch, even though he’s filling the zone with it. All those heaters located inside the zone combined with all the additional whiffs has led to the 14th-highest CSW (called plus swinging-strike rate) among all four-seamers thrown at least 100 times.

If there’s one problem with his fastball, it’s what happens when batters do make contact with the pitch. Thus far, he’s allowed a .317 wOBA on contact off his heater, but the expected wOBA on contact is far higher at .446, with a 47.4% hard hit rate and a 13.2% barrel rate. A flat fastball will be effective in the zone no matter where it’s thrown, but it’s most effective up in the zone where it will “jump” over a batter’s swing. As you can see in the table above, the average vertical location of his fastball has dropped slightly this year. If he’s able to locate it consistently up in the zone again, I suspect some of that hard contact will turn into pop ups and lazy fly balls instead.

If Castillo is committed to locating his fastball in the heart of the zone to generate as many whiffs as he can, his secondary offerings provide him with the contact management his fastball is currently lacking. Both his changeup and his slider have an expected wOBA on contact right around .300, giving him two pitches to use if he needs to generate weak contact. That’s despite those two secondary offerings running nearly identical 25% whiff rates, career-lows for both of them. For whatever reason, his secondary offerings have lost a ton of effectiveness this year, but he’s made up for it with his suddenly elite fastball. Moving forward, you’d expect his changeup and slider to rebound a bit since there are really no significant physical changes to them. If that happens, he’ll have three fantastic weapons in his arsenal to help him continue racking up strikeouts.

Because Castillo will be under team control through 2023, the cost to acquire him will be extremely high. Whichever team does end up trading for him will be getting an excellent pitcher who has made key adjustments to unlock a new level of performance.