A week ago, the Yankees faced off against the Red Sox with Aaron Cook on the mound. Cook isn't exactly a hard thrower, which makes him extremely hittable. Teams have done a good job of hitting him this season, to the tune of a 5.18/5.16 ERA/FIP and a whiff rate under four. When Cook faced the Yankees, he threw nine fastballs in five innings of work. Of those nine fastballs, batters swung and missed at only two of them. In CC Sabathia's last start against the Rays, he threw 34 fastballs. Batters swung and missed at only two of them.
CC Sabathia is not Aaron Cook, but in this one case, he was like Aaron Cook. Even in a down year, which it is since there's a way to put Sabathia's name next to Cook's and have it mean even a little something, he's been a key and valuable player in the rotation. This season has been a bit disappointing, though. It's tough not to be a little down after an offseason that saw him sign off on an ace-like extension. When a guy is expected to be the ace now and for a couple years after, an Aaron Cook-ian fastball isn't something we want to see, even if it was only one start. It's one start too many to be like that.
Sabathia has been hurt, yes, but that doesn't seem to fully explain his jump in numbers. At least it doesn't explain it without access to his doctors and various medical chart-type things. A lingering or hidden injury could be hurting his performance, but the accessible stuff points to a declining fastball. It doesn't spell doom by any means since most pitchers have to adjust as they get older, but so far the adjustments either aren't there, or just aren't working.
Maybe we should have seen this coming. I mean, not this exact thing, but some drop in performance probably should have been expected. Sabathia is in the middle of his age 32 season and had over 2,300 innings on his arm coming into the year, after all. Durable workhorse or not, that kind of inning load will eventually take its toll. After his first season in New York there was a slight dip in fastball velocity, but this season he's lost over one-point-five miles per hour off his average fastball from that time. (92.4) Just for the sake of comparison, A.J. Burnett lost one-point-five miles per hour off his fastball during his time with the Yankees. Without that extra velocity, batters are missing less, and squaring him up more.
June was a good month (35.2 IP, 3.03/2.12 ERA/FIP) which isn't all that surprising considering that was his highest whiff/swing rate over a full workload month. And while he had other stretches of quality pitching, what's concerning is that the baseline for hitters swinging and missing has gone south. September has spiked up to 15.1 percent whiffs on his fastball, but if his last start, and really this whole season, is any predictor, that could easily correct in the wrong direction. Batters are already slugging over 100 points higher against his fastball than in his worst year in New York (.580), so any kind of backwards correction could be really ugly.
OK, this happens to most pitchers who work off the fastball at some point. The fun is in changing things up to combat the decline. Changing things up; that's a good way to talk about this because it's part of the problem. Part of what makes Sabathia great is how well he can mix in his secondary offering. Start a good chunk of the time with a fastball and work off that with a slider, sinker and changeup mix. That's strangely stopped happening this season.
I really shouldn't say his mixing is strange since that too has been happening for a couple years. The fastball hovered around 45 percent from 2009 to 2011, but the slider usage has been on the rise at the expense of his sinker and change. Now the slider is starting to take away reps from the fastball, giving him a 40 percent fastball, 34 percent slider, 15 percent sinker and 10 percent changeup mix. In a span of three years he's morphed into a quality, slightly less predictable and competent against the other side of the plate version of Boone Logan.
That's a little harsh. He isn't Aaron Cook and he isn't Boone Logan. Imagining Sabathia as some hybrid of Cook and Logan is depressing on the baseball level and terrifying on the human level. It's understandable that he'd want to work the slider in more often as hitters have struggled to slug higher than .230 against it for his career. The understood isn't always a good thing, though. Especially against lefties, he's become predictable, throwing the slider over half of the time regardless of situation. The pitch works, but if the hitter lays off the slider, they can, and have, sit fastball and mash. (.816 SLG) Righties mash the fastball less (.512), but even then, if Sabathia falls behind they can wait for it with the slider basically abandoned. (12 percent) When the fastball continues to be located up with declining velocity and hitters can sit on it, it's going to be bad news for any pitcher.
It's hard to believe that lasting effects of a couple injuries has affected his pitching style in such a drastic way. Given how much extra strain throwing a pile of sliders puts on an arm, you'd think a pitcher nursing an injury would shy away throwing more. A completely uninformed outside viewpoint is of a pitcher trying to figure out what works as overpowering velocity begins to betray him. ‘Ace' or not, Sabathia is still very good, very valuable and will be a key piece going forward. What's happening now isn't doom, but it isn't exactly calming when thinking about the back end of the contract either.