By the end of May, Luis Castillo had given up at least five hits in all but one start, finishing the month on a seven-game losing streak with a 7.22 season ERA. After being one of baseball’s most consistently solid starting pitchers over each of the past three seasons, he’d suddenly become perhaps the game’s most consistently hittable one. At the time, the likely-selling Reds’ most valuable player in a potential trade had lost almost all of his value.
However, in June Castillo turned it around, finishing the month with just six earned runs across 31.2 innings in five starts, lowering his season’s ERA mark to a still-unsightly 5.14. Like clockwork, he continued his roll through July, again recording six earned runs across exactly 31.2 innings, lowering his season’s ERA another run to a semi-respectable 4.20.
Since overcoming his early struggles, Castilo’s seen his fastball velocity climb back up towards his career average of around 97 mph, from just around 95 mph at the season’s start. Also, his slider’s matched its effectiveness of past seasons, netting whiffs on 40 percent of swings or better in each of the past three seasons. Even better, since the start of June, his strikeout rate has been 29 percent, right in line with his numbers from the last two years of 30.5 percent and 29 percent, respectively.
However, one metric of concern is Castillo’s inability to earn swings and misses with his signature changeup, the pitch he still throws more than any other. After missing bats on greater than 40 percent of swings in each of the past four seasons, Castillo’s changeup whiff rate has fallen to just 30.3 percent, while the pitch’s put away percentage has fallen all the way to just 16.5 percent after recent rates of around 30 percent.
Since his struggles have inversely coincided with MLB’s foreign substance ban crackdown, it’s not as if decreased spin rates are limiting his ability to deal with his changeup. In fact, his changeup’s movement profile matches that of last year’s almost identically. Even though he doesn’t throw it nearly as much as his changeup, especially to lefties, it’s the slider that’s salvaged Castillo’s season, netting him a run value of -10 according to Statcast compared to his +3 mark for the change.
Considering his several-seasons-long track record of pitching dominance, it seems reasonable to assume that Castillo’s early slide was more aberrant than his recent string of successes. In the two seasons prior to this one, Castillo cleared more fWAR than all but 10 other starting pitchers. Even if batters have figured out his changeup to a certain degree, his solid fastball and awesome slider have buoyed his value as a pitcher.
Assuming his new norm of dominance will continue to match his old norm of the same, Castillo could likely net a hefty return in a deadline deal, especially considering the fact that he’s arbitration-eligible in each of the next two seasons, taking him past the age of 30. While the Yankees probably don’t have enough on the farm they’d be willing to move for Castillo in addition to a bat, they could certainly put together a competitive package for one or the other.