The Astros Need to Solve Masahiro Tanaka’s Slider
If Masahiro Tanaka has a signature pitch, it’s his slider. When he first came over from Japan in 2014, nearly half of his strikeouts came on the splitter despite throwing it only a quarter of the time. In his first three seasons in the majors, Tanaka threw his splitter more often than any other pitch and batters put up a feeble 37 wRC+ against it, while whiffing on the pitch 19% of the time. But in 2017, Tanaka used his slider more often than the splitter. In 2018, that trend continued; he got better results from his slider than he did with the splitter. This season the disparity in usage and effectiveness grew. Tanaka struggled with his splitter due to changes in the baseball, but even after re-configuring the splitter in July, his slider has remained his best pitch.
Against the Astros in Game 1 of the ALCS, Tanaka got eight swings and misses. Every single whiff came on the slider. Here’s how Tanaka’s usage of his slider has compared to that of his splitter this season: