The splitter is likely Masahiro Tanaka’s most important pitch. However, so far through 9 starts this year, he has thrown that pitch fewer than at any point in his career (21.9-percent). The value per 100-pitches of his splitter is also by far the worst of his career at -3.95. This number essentially accounts for the number of runs above average that a pitcher has saved with that pitch.
Movement
The below graphic depicts the movement of Tanaka’s pitches from each of the past three seasons. The gear-like shapes represent league averages. The teal-colored shapes represent the splitter.