His entire career, James Shields has always been known for his fastball-changeup combination. But this season, there has been an interesting phenomenon going on with his cutter, which is arguably his fourth-best pitch behind his changeup, his fastball, and his curveball. According to Brooks Baseball, Shields has used his cutter 22% of the time this season, the highest ratio of his career. Overall, Shields has used it about 23 times per game and it has been a slightly below-average pitch, with hitters being 3.76 runs above average against it on the season, an average of .13 runs above average against it per game using linear weights. (Above-average favors hitters, below-average favors pitchers.) On the year, there has been basically no correlation between how often Shields has used the cutter and how well he has performed in his starts both in terms of ERA and FIP. But how effective his cutter has been has had an enormous impact on how well Shields has performed. On the year, the effectiveness of the cutter in his starts has a .50 correlation with his start ERA and a .45 correlation with his start FIP. That doesn’t seem like the biggest deal- only 25% of the Shields’ ERAs in his starts and 20.25% of Shields’ FIPs in his starts. can be explained by a linear relationship with his cutter. But this is his fourth pitch we’re talking about! This isn’t something that’s occurring by chance- there’s just a .003 probability that the correlation between Shields’ ERA and the linear weights for his cutter happened by luck alone and a .007 probability for Shields’ FIP and his cutter effectiveness.
On Sunday, James Shields had himself an incredible start, allowing just 2 hits as he tossed a complete-game shutout, striking out 8 while walking none. According to linear weights, Shields’ best pitch was his fastball, coming in at an incredible -3.81 runs below average, but his second-best pitch was not his changeup or his curveball but his cutter, which was 1.81 runs below average. It was a near-perfect example of how Shields’ cutter may not be one of his headlining pitches, but it has the ability to be an extremely good complementary offering. On the season, Shields’ cutter actually a swing-and-miss rate below league average, 8.05% compared to the 10.25% league average. But he has been able to throw it for strikes, tossing it for a strike 66.17% of the time, right behind his 67.43% mark for his fastball, and use it to force quite a few groundballs when it’s on.
Shields’ cutter is not a pitch that’s going to rescue him when his fastball and changeup are off. On July 15th against the Red Sox, Shields had one his worst starts of the season, allowing 6 runs on 11 hits in just 5 innings, striking out 5 while walking 3 and allowing 2 home runs. He used his cutter 31 times and it was extremely ineffective, making a bad situation worse. There are times this season where you couldn’t help but shake your head and wonder why in the world Shields was using his cutter in such big spots. But when his fastball and/or his changeup are working well, Shields’ cutter give hitters another pitch to think about and can be a very effective pitch. In Shields’ two shutouts this season along with the 8 shutout innings he tossed against the Red Sox on April 16th, hitters were 4.80 runs below average and Shields’ cutter.
James Shields will always live and die on his fastball and changeup. But this season he has started to establish his cutter as another pitch for hitters to think about. It’s never going to be a big swing-and-miss pitch and when Shields tries to depend on it too much, he gets hit hard. But as a pitcher who throws his changeup an inordinately high percentage of his time and throws his fastball around the lowest percentage of the time in baseball, he has to maximize the effectiveness of his other pitches in order to succeed consistency. Because of that, the success and failure of Shields’ cutter will always be a factor for him moving forward. Hopefully he can mix in his cutter effectively as he continues his great pitching of late into the rest of the season and into the playoffs.