Starting off this season, CC Sabathia had issues maintaining regular sink on his fastballs. In the span of 5 starts from April 17 to May 10th, the lefty corrected his problems by “getting on top of the pitch”, going 5-0 with a 2.52 ERA, an 8.69 K/9, a 1.14 BB/9, and a 6.68 H/9 in 39.1 IP. Despite pitching against some weak offenses in his 3 starts from May 15th to May 26th, he has gone 1-2 with a 4.05 ERA, a 7.2 K/9, a 4.95 BB/9, and a 9.45 H/9 in 20.0 IP. Strikeouts have been falling while walks and hits have been increasing in a very un-Sabathia-like fashion. I wouldn’t call his recent starts bad, but he hasn’t produced as an ace should, and there are some key issues haunting the southpaw.
As I mentioned above, the struggle in his first couple of starts this year were largely due to an inability to replicate the spin on his sinker and four-seam fastball. In his most recent starts, he’s shown similar tendencies with his four-seam fastball. Again, it appears as if Sabathia is pulling the fastball instead of getting on top of it, which is creating greater horizontal movement into left handed hitters. In the 5 start range of 4/17 to 5/10, his four-seam had a spin angle of 160 degrees and a spin rate of 2,040 RPM. From 5/11 to 5/26, the spin angle has dropped 6 degrees to 154, and the spin rate is up 100 RPM. While this doesn’t individually suggest a troubled fastball, the graphs below show the slight difference in how the pitch is moving.
In the two graphs above, the trajectory of Sabathia’s four-seam fastball is plotted from the pitcher’s mound on the right to homeplate on the left. I apologize for the lack of contrasting color; they were pretty brilliant until the file was converted. If you zoom in, you can see that two different trajectories exist, one in red tracing the average four-seam from 4/17 to 5/10, and the blue one tracking the four-seam from 5/11 to 5/26. The bottom image shows the vertical movement, or the “sink” or “rising” action of the pitch, and you can see the lines are nearly identical. Instead, focus on the top image, which is a bird’s eye view of the horizontal movement. As you can see, the pitch break varies by a couple of inches.
Here we have the movement of the pitch based on a catcher’s perspective, with the origin of the graph being a no-spin pitch conforming to gravity. Again the red pitches are from his successful 5 starts (4/17 to 5/10) and the blue are from his recent 3 starts (5/11 to 5/26). While both data sets of movement have similar vertical ranges, the horizontal is quite different. The pitches in red more often fall closer to the y-axis, around an inch to 5 inches, while the blue pitches are around 3 to 7 inches away. The average difference is more than an inch more movement into left handed hitters in his recent starts, the difference between 3.47 inches in his successful 5 starts, and 4.79 inches into lefties in his recent 3 starts.
A couple of inches are enough to miss your spots, and indeed Sabathia has been doing a lot of that lately. Not only are his walk numbers up, 11 walks in his 20.0 IP, but he’s given up 4 homeruns in that same time period. Two of the homeruns came on the four-seam, and the other two came on the sinker, which is showing very similar control problem. Hopefully he can fix his erratic movement by getting on top of the fastball as he did in mid-April, and thus maintain the correct spin angle.
Unlike the increase in walks, the decrease in strikeouts appears to be a slider issue.
Here we have the trajectory of the slider traced in green for his 5 successful starts from 4/17 to 5/10, and traced in red for his 3 most recent starts from 5/11 to 5/26. In the top image, a bird’s eye view, the slider from his more successful starts has considerably more break away from left handed hitters, especially in the last 20 feet from the plate. We see the opposite scenario in the bottom image, which shows the slider having slightly more vertical break starting around 30 feet from the plate, where the two lines begin to matchup.
The difference is even more clear using pitch movement, which has the 4/17-5/10 slider moving anywhere from 2 to 7 inches away from left handed hitters, and the 5/11 to 5/26 slider moving in a much larger spread horizontally. Vertically, the slider in red sees up to 5 inches of sink at times compared to the no-spin pitch. The slider from his 5 successful starts never dropped below the x-axis. While more vertical movement doesn’t necessarily mean less success, he is trading the impressive horizontal movement for a straighter pitch that sinks more. The 4/17 to 5/10 slider averages 1.25 inches of vertical movement above the no-spin pitch, and 3.19 inches away from left handed hitters, compared to the 5/11 to 5/26 slider averages 0.15 inches of vertical movement and only an additional 1.79 inches of horizontal movement away from lefties.
Again, the difference between movements comes from the spin angle and rate, which was much more uniform in his more successful starts. The difference of spin angle for a slider is more complicated than a fastball, although Sabathia seems to have his most successful one between 240 to 300 degrees. The slider from his most recent starts have ranged all around the spectrum, sometimes throwing the pitch with the high angles associated with curveballs for southpaws. Along with spin angle, the spin rate dropped around 130 RPM in his most recent starts, which lowered the Magnus effect on the ball, and thus decreased the pitches’ movement.
While Sabathia can fix the fastball with some delivery technique’s he’s already had success with, the slider will probably continue to vary. The current problems have cut the whiff rate on the slider in half, but perhaps he’s best left to solve these issues now, rather than September or October.