One of the great debates in baseball right now is whether Joba Chamberlain should be a starter or reliever. To me, it comes down to simple math. A major league baseball team will pitch about 1425 innings each year – so the object would be to get as many quality innings in those 1425 as you can. This is why a starter who pitches 200 good innings is aways worth more than a reliever who pitches 70 good innings.
So, what is Joba Chamberlain worth as a starter? As a starter, his career ERA is about 3.30 – which is about a run and a half per nine better than the average AL pitcher. This year, his ERA is 3.81 despite pitching in that horrific launching pad that is new Yankee Stadium. Assuming he pitches about 180 innings, he’d save the Yankees 28 runs over what the average pitcher would allow in a season. (180 / 9 x 1.4 = 28).
Let’s assume that, as a reliever, Joba pitches 72 innings of relief. To make it an even switch, Joba’s ERA would have to be about 3.5 runs less than the average pitcher (28 / (72/9)). Basically he’d have to maintain an ERA of about 1.25.
Is that likely? Probably not. As such, Joba Chamberlain should remain a member of the rotation where he gives the Yankees the most good innings and has the greatest effect on winning games.