It's easy to forget just how good Hiroki Kuroda was in 2013. From April 3rd until August 12th, Kuroda was not only the Yankees' best pitcher, he was a legitimate contender for the Cy Young award with a 2.33 ERA over his first 154.2 innings. Over his last 8 starts, Kuroda looked like he ran out of juice. The 38 year old pitcher owned a 6.56 ERA over those 46.2 innings, yet his strikeout rates continued to accumulate. Kuroda finished the 2013 season with a 3.31 ERA, but it's not easy to convince Yankee fans that he'll be capable of replicating that in 2014. His demise this August and September was similar to his late-season regression in 2012, and now we're left wondering if Kuroda is too old to throw 200 major league innings. To get to the bottom of Kuroda's drop off, we should look to his walk rates. In his first 25 starts of the season, Kuroda walked just 29 batters, yet in his final 8 games, he walked 14. Command was an obvious issue for the right-hander, but why? The PITCHf/x data shows that Kuroda's issues were not velocity related, as he gained anywhere from .5 to 1 mph on his velocity by the end of the year. The biggest difference for Kuroda was his pitch movement, which significantly decline in his final 8 starts. While he averaged about 8.5 inches of movement into right-handed hitters and 6 inches of vertical rise on his sinker at the beginning of the season, that movement dropped to 7 inches horizontally and 2 inches vertically in his last 8 starts. His slider also lost 4 inches of vertical movement, and his splitter an inch and a half of horizontal movement.
While this could be age related regression, it's very unlikely that he'd suddenly lose the feel for pitching in the matter of a game. More than likely, Kuroda is dealing with some sort of injury in mid-August. Kuroda did have some hip soreness in the beginning of July, which could have affected the pitch movement.
There are few signs of mechanical issues with Kuroda in September, in fact, in this particular pitch he has a more balanced stance. Between his hip rotation and arm slot, Kuroda looks exactly the same, which makes it difficult to pinpoint what happened to his movement.
With different movement, Kuroda struggled to command his pitches. According to Alec Dopp's piece at BaseballAnalytics.org, PITCHf/x data also shows that the frequency of pitches moved down and in towards the right-handed batters box at the end of the season. With decreased vertical movement on his pitches already, this is a sign that Kuroda wasn't finishing his pitches and under-rotating during his delivery. Considering the injury in July was to his lead hip (left), it's very possible that this injury contributed to his lack of rotation at the end of the year. This could also be why there was less momentum and thus better balance in the later half of the GIF above.
If this is indeed the problem, simply a sore hip, and assuming we're not talking about labral tears, there's little reason to think that Kuroda won't recover in 2014. Yet such declines in movement are major red flags for both elbow and wrist injuries. In the chance that Kuroda has damaged a ligament in his arm, the right-hander could be in major trouble for 2014. Fortunately, the Yankees had the opportunity to give Kuroda a physical before re-signing him this offseason, so odds are that the injury isn't this severe.
As we continue this projection series, I've strived to be realistic with my numbers. For Kuroda, I expect him to pitch to about a 3.50 ERA with a 3.60 FIP, but I doubt he'll reach 200.0 innings. While this could be considered an optimistic projection based on how he finished 2013, I feel confident in the decline of his pitch movement being injury based, and my money is on it simply being a sore hip. In that case, Kuroda is fully capable of being the ace-type pitcher he was in the first 25 starts of 2013.