Lost amid the signings of Jacoby Ellsbury and Carlos Beltran as well as losing Robinson Cano to the Seattle Mariners, the Yankees retained one of the few bright spots in 2013 by re-signing Hiroki Kuroda. As Jeff Sullivan pointed out, Kuroda pitched better last year than all of the other available free agent starters, and the Yankees only had to guarantee one year for his services. The move did not draw much attention, but that will happen when it was expected and coincided with the team losing its franchise player.
Despite pitching very well in 2013, the signing was not without risks. Kuroda faded badly down the stretch, and some questions arose whether Kuroda might be finished. Chris Mitchell took a look at some of Kuroda's peripheral stats and concluded the problems were likely the result of bad luck and not poor pitching. Our friends over at Beyond the Box Score investigated the numbers and reached the same results. While Kuroda's poor home stretch may have been a result of bad luck, age catches up to all players and a decrease in performance is expected over time.
Kuroda is far from the only pitcher to pitch effectively into his late 30s so perhaps examining those players may be instructive in predicting what the Yankees will receive during the 2014 season. Between 2011-2013, Kuroda's age 36-38 seasons, Kuroda put together a bWAR of 12.7 over 623 innings pitched. Using the play-index feature at baseball-reference.com, I searched for a group of pitchers over the last 50 years with at least ten bWAR over their age 36-38 seasons and 500-700 innings pitched. The search resulted in around a dozen players, but to ensure the players were similar, I removed pitchers who did not pitch well in their age 38 seasons. Between bWAR and fWAR, Kuroda averaged 3.95 WAR last season. I removed any player that was not above an average WAR of 3.0.
Unfortunately, narrowing the list of players left only four pitchers. Four is not enough to draw great conclusions, but it does provide a greater appreciation for Kuroda's efforts over the last several years. The four similar pitchers are Roger Clemens, Rick Reuschel, Geoff Zahn, and Tom Glavine. The four pitchers averaged 11.5 bWAR over their age 36-38 seasons, including an average bWAR and fWAR of 4.2 during their age 38 season. In their age 39 season, the quartet held on fairly well, averaging 2.8 WAR. Only Geoff Zahn did not pitch well, making only seven starts before a shoulder injury and subsequent surgery ended his career. Clemens (pitching for the Yankees), Reuschel, and Glavine all had seasons at 3.5 WAR or above which bodes well for Kuroda's prospects next year.
Interestingly, both Reuschel and Glavine faded down the stretch in their age 38 seasons like Kuroda, but both were able to rebound the following season and pitch well. Yankees General Manager Brian Cashman stated before the off-season started that he was looking to add 400 innings to the rotation. His goal is halfway completed. With a rebound from CC Sabathia, continued development from Ivan Nova, and another solid season from Kuroda, the Yankees rotation could again prove to be a strength next season.