Coming into this season, it seemed CC Sabathia's main weapons were a mid-90s fastball and a sharp, deceptive slider. But this year has been a bit different: he's using his changeup (and fastball) with greater effectiveness than ever before. In fact, his changeup is the best in the entire American League, while his fastball ranks fifth best.
His pitch selection has been quite different from the previous two years - he's throwing fewer sliders (20.1%) and changeups (17.8%) than in either 2007 or '08. That naturally means that he's throwing more fastballs, which he is (62.1%).
What's most surprising is that his fastball is better than it's ever been. According to FanGraphs, his fastball has saved .59 runs for every 100 times it's been thrown. It was never better than .47 in any previous season.
His fastball is enjoying a symbiotic relationship with his changeup, which is also more effective than at any previous time (saving 3.65 runs/100 thrown). This makes sense, as the fastball sets up the changeup, and vice versa. But why are these pitches so effective this year while the slider is not? I have a few theories:
1. Perhaps it's being mandated from Girardi/Cashman because breaking pitches are more stressful on the arm than fastballs/changeups, and in the first year of a (potential) seven-year deal, the Yankees want to ensure Sabathia's long-term viability.
2. Another is that his slider is just not as effective as in years past (a scary though that could mean injury), so he's had to use it less. This one I don't believe (or don't want to).
3. Maybe his slider was so good last year (3.56 runs saved/100) that the book on him may be to look slider - realizing that, he's resorted to using the changeup as his out-pitch.
4. The last theory is simply that his changeup is better now. It has improved each of the last five years, and he has more than 2000 pro innings under his extra-large belt, so it's reasonable to assume he's been improving it and that it's now surpassed the slider as his best pitch.
Or it could just be all of the above. Whatever it is, keep throwing it CC.