Hiroki Kuroda is in the midst of his 3rd season as a Yankee. The series of 1 year deals have given the team flexibility in managing payroll commitments and the player the ability to return to Japan when ready. Kuroda has been extremely productive in his first two full seasons in New York. He was worth 3.7 fWAR and 5.5 RA9-WAR in 2012. Those figures were 3.8 and 4.6 in 2013. The fWAR is based on FIP which focuses entirely on what a pitcher can control (strikeouts, walks, and home runs) without respect for balls in play and sequencing. RA9-WAR, on the other hand, takes all runs a pitcher allows (both earned and unearned) into account. This version of WAR gives Kuroda full responsibility for all balls in play and the sequencing of the events that occur while he is pitching. By both metrics, Kuroda has been one of the top pitchers in baseball the past two seasons. While he has tailed off at the end (likely due to age and mileage on his arm), Kuroda has been a resounding success in New York.
Through 11 games started and 65 innings pitched this season, however, Kuroda has struggled when looking at raw runs allowed totals including ERA (4.57) and RA9-WAR (0.0). At first glance, Kuroda appears to be having a rough season for the first time in his MLB career. Digging deeper, Kuroda is doing the same things that have led to success his whole MLB career. His strikeout rate is a tad lower than the past two seasons: 17.3% compared to 18.2% and 18.7% the past 2 seasons. The walk rate is also lower. A 3.9% BB walk this year compared to 5.2% and 5.7% the past 2 seasons. He has traded a few less strikeouts for a few less walks which is backed up by his highest in-zone% (42.9% pitches in the strike zone) as a Yankee. His K%-BB% (a better measure than K/BB ratio) is 13.4%, higher than his past 2 seasons and 43rd highest in MLB this year. The 3rd input into FIP, home runs, is where Kuroda has gotten into trouble. His HR/9, 1.25, and HR/FB, 12.3%, would both be the highest of his career. xFIP (just taking into account walks and strikeouts, not homers) might be a better metric here because home runs allowed have been shown to be fluky from season to season. The 3.61 xFIP he is running this season is very good. Regardless, Kuroda’s HR/9 is likely to regress as the groundball percentage (47.2%) is right in line with his career norm and the luck should even out. Another aspect of Kuroda’s unluckiness is his BABIP allowed. It is all the way up at .311 despite never having a season above .300. There is really no reason to believe his true talent at limiting hits on balls in play has eroded this much. He is getting unlucky while pitching in front of a terrible infield defense as a groundball pitcher. Finally, the last aspect of unluckiness is his LOB%. His career LOB% is 72.7% (right around the league average), but this year it has dropped all the way to 63.7%. When runners get on base against Kuroda, they are likely to score.
Unluckiness explains most of Kuroda’s inability to prevent runs so far this season. As long as Kuroda’s peripherals stay about the same his FIP-ERA gap will close and he will start limiting runs at an above average rate again. His areas of unluckiness don’t even have to regress to Hiroki Kuroda levels. Regression towards the league mean for his HR/FB, BABIP, and LOB would give the Yankees an above average starting pitcher for the season. He is especially vital to the Yankees’ rotation success this season with CC Sabathia, Ivan Nova, and Michael Pineda injured and a lack of elite pitching prospects in the upper minor league levels.