So far this season the Yankee bullpen has lived up to its preseason hype. The Bronx relievers have a combined ERA of 3.07, which is ninth-best in all of baseball and third-best in the American League. In 138.0 innings of relief work, the Yankees have allowed only 123 hits and 60 walks, which translates to a WHIP of 1.33. To put this performance in perspective, CC Sabathia has an ERA of 3.06 and a WHIP of 1.30 so far on the year.
Unfortunately, this strong performance may not be sustainable. With Rafael Soriano on the disabled list, Joe Girardi has been turning to Joba Chamberlain, David Robertson and Mariano Rivera more than any other relievers on the team. As a result, all three are on pace to pitch an ill-advised numbers of innings.
Robertson currently projects to pitch 66.1 innings this year. Chamberlain is on pace to pitch an astounding 85.1 innings this season. Rivera is on pace to pitch 74 innings this season, and is also 41 years old. Each of these totals would represent bullpen abuse for the respective pitcher.
Of the three, Robertson’s current level of usage is most sustainable. While 66.1 innings would represent a new career high for the right hander, it would not be a substantial increase from his current career high of 61.1 innings, which was set in 2010. The same cannot be said for Joba. Flat out, Girardi needs to use Joba less. Chamberlain has never logged anything close to 85 innings of work as a reliever. Last season the Yankees called on Chamberlain to pitch a then career high 71.2 innings of relief work. Joba’s rate of usage this season represents a twenty percent increase on his work load last season. That’s a dangerous proposition for a pitcher with Chamberlain’s injury history, which is why Joba was unavailable to pitch during the first game in Baltimore this past week.
While the current demands on Chamberlain and Robertson are concerning, at least those two pitchers are young and presumably durable. Mariano, on the other hand, is an old man (for a ball player). As a result, his usage has reduced each season since 2004. That year he logged 78.2 innings of work. He has steadily been called upon less and less each season since then, until in 2010 he pitched only an even 60 innings, the second fewest of his career.
If the current rate of usage continues, Mariano would pitch the most innings that he’s pitched since 2006 and would record his first season-over-season increase in innings pitched since 2004. An increase in innings pitched from 60 in 2010 to 74 this season represents a year-over-year increase of nearly 25%, and a sure fire recipe for an injury.
Fortunately, in his short tenure with the Yankees Joe Girardi has demonstrated a willingness to rest his best relievers and distribute work evenly among all his arms in the ‘pen. So far it looks like that trend will continue in 2011. Girardi found time to rest Chamberlain and Robertson this past week, and with a little help from the offense hasn’t had to use Rivera since Wednesday. If Girardi is smart, he’ll continue to find more time to rest these three arms. He may not have a choice because if trends continue for the rest of the season he risks injuring one of his best young relievers, or the greatest closer of all time.