On Kuroda's Hip Injury

During last night's game, we learned that Hiroki Kuroda sustained some sort of leg injury and wouldn't make his start on Friday. Lately, this type of news has been a death sentence, but fortunately the MRI came back clean. Kuroda has tightness in his left hip flexor, something that hebegan to feel before his start in Baltimore on Sunday. While this is the sort of injury that should heal itself, I was curious to see how it affects his pitching. In his last start, Kuroda was unspectacular. He gave up 7 hits, 3 of which were home runs, 4 earned runs, and 7 strike outs in 6.0 innings. Those three home runs make up 25% of his total for the year, so I suspect his hip played into these home runs somehow.

Looking at the PITCHf/x data, Kuroda showed an overall drop off in horizontal movement during this start. Where his four-seam sat at 4.5 inches in to right-handed hitters this season, it only showed 3 inches on Sunday. Likewise, his sinker and splitter showed 2 fewer inches of movement.

I decided to take a look at a sinker from his Sunday start and compare it to a sinker from the previous start against the Rangers.


The sinker in red represents the pitch from Sunday (while his hip was acting up), while the pitch outlined in blue is from his previous start. You can see that there is a lack of depth to the sinker, as the pitch breaks less into to the right-handed batter's box.


This injury should be easy to recover from, and it's good to see that his last performance was probably a product of poor pitch movement.