https://blogs.fangraphs.com/red-sox-fill-out-rotation-with-intriguing-michael-wacha-addition/
Wacha succeeds or fails with his changeup. It allowed a .270 wOBA last year, and he’s thrown it over a quarter of the time in the last two seasons. It’s his best swing-and-miss pitch, with a SwStr% of 19.6%, though honestly, it’s his only swing-and-miss pitch; his fastball, cutter and curveball get whiffs less than 10% of the time. He throws his change in the upper 80s, about 7 mph off of his fastball, and with its decent arm-side movement plus an average amount of drop, it can be lethal below the knees to lefties. He throws it more than 25% of the time to righties as well, and its effectiveness only slightly drops against them (a .262 wOBA to lefties and .275 to righties).
But even Wacha’s nasty changeup isn’t immune to the long ball; its HR/FB rate last season was 24%, the worst of any of his pitches. Like most changeups, it leads to a lot of ground balls, but last year, it had a career-low GB% (49.5%), career-high FB% (24.8%), and career-high launch angle (8 degrees). A lot of this change in results, though, seems to have come from hitters being in better position to elevate balls in the lower third of the strike zone.
Beyond his changeup, the real issue for Wacha the last couple years has been his cutter. He’s increased its usage over the last two years, all the way up to 27.2% in 2020 and 24.8% in ’21. But hitters tore it apart last year to the tune of a .415 wOBA allowed, and according to our pitch value metric, it’s been a negative his entire career, with the lone exception being the 2018 season.
Wacha and the Rays seemed to have concluded that his cutter was a lost cause, because in mid-August, its usage dropped; from August 28 onward, he threw only a small handful. His performance during that cutter-less stretch, you ask? A 2.88 ERA and 3.29 FIP. That’s the stretch that earned him this contract, and it would seem obvious that his cutter will stay missing next season in Boston — or that might be premature, as Wacha stated recently that he plans on bringing it back.
Wacha looked like a completely different pitcher late in the season without his cutter, with its usage distributed to a newly developed sinker and his curveball; both of those pitches went from basically unused to each being thrown more than 10% of the time. The sinker is a logical replacement, given its low spin rate, and the early returns seemed positive, as it allowed a .333 wOBA. It’s hard to draw a sweeping conclusion on it after this limited sample, though, and the same can be said for his curveball, which was hit quite hard (.425 wOBA) in its limited run, though none of that came in the form of extra-base hits, and it had an absurd 71.4% ground-ball rate. It will be interesting to see what kind of arsenal he brings to the table in 2022 after an offseason of tinkering with these pitches and working with a new staff.