The Return of Cahill’s Curve by Chris Cwik April 5, 2011 Warning: The content of this post breaks two major rules recently laid out by the FanGraphs writing team. It’s a post about stats from last week, and it validates the first prediction in Matt Klaassen’s recent post. You’ve been warned, now proceed at your own risk. Despite posting an ERA of 2.97, and winning 18 games last season, Trevor Cahill entered 2011 as one of the major regression candidates due to some poor peripherals. One of the most puzzling aspects of Cahill’s young career, and one of the reasons analysts are calling for regression, has been Cahill’s low strikeout rate in the majors. Over his minor league career, Cahill struck out 9.9 hitters per game. In the majors, however, Cahill has managed to strike out only 5.12 batters per nine innings. One theory behind Cahill’s struggles in the majors deals with the use of his curve ball. Minor league scouting reports rated Cahill’s curve as a true wipe-out offering. Once he reached the big leagues, however, he stopped relying on his curve. Well, the curve, and the strikeouts, returned in Cahill’s first start of the 2011 season. Unfortunately, those two facts have little to do with each other. Last season, Cahill relied on his curve 13.6% of the time according to his PitchFx page. Of the 105 pitches Cahill threw in his start last week (and again, it’s a tiny, tiny sample), Cahill threw 24 curve balls, good for 22.8% of his pitches thrown that night. While early scouting reports might suggest Cahill’s increased usage of his curve led to his strong performance in the strikeout department (8 in 4.2 innings pitched), a quick look at his start reveals that’s not exactly the case. Of his eight strikeouts, only two of them came via the curve. Cahill was given the inside corner vs lefties most of the night, and capitalized by getting four called strikeouts with his sinker. The other two strikeouts came via Cahill’s changeup. So, if Cahill didn’t utilize the curve as his strikeout pitch, what effect did it have during the game? The main culprit behind his high pitch count may have been defensive misplays that extended innings, but Cahill’s curve may have contributed to his lack of efficiency as well. Out of the 24 curves thrown by Cahill, 6 were balls, 8 were strikes, 7 were fouled off, 2 led to hits, and 1 led to an out in the field. With two strikes, those numbers become: 1, 2, 3, 2 and 0. Using that data, we can say that 13 of Cahill’s 24 curves led to a successful result (8 strikes, 4 fouls led to strikes and didn’t extend at-bats, 1 out in the field). It’s the other side of the equation, however, that is somewhat concerning. With two strikes, Cahill’s curve wasn’t as effective. While he managed to strike out two batters, he also allowed three batters to extend their at-bat, which led to Cahill throwing more pitches. Again, it’s only one game, but the Mariners were able to fight off Cahill’s curve and extend their at-bats. When your defense commits four errors behind you, those extended at-bats really start to exacerbate your pitch count. It’s not all gloom and doom with Cahill’s curve, though. The fact that he was willing to use it often will probably help him fool hitters over the course of the season. In his first start of the season, however, his increased usage of the curve did not lead to his high strikeout rate. It actually allowed Mariners’ hitters to extend innings and make Cahill throw more pitches. That’s not to say the curve won’t end up fulfilling it’s destiny as Cahill’s strikeout pitch, we just shouldn’t assume there’s a correlation at first glance.