Extra Mustard By Baseball Prospectus

WITH ADAM WAINWRIGHT on the verge of bullpen stardom (11 strikeouts, no runs allowed in seven innings during the postseason), should the Cardinals continue to use him as a reliever or turn him back into a starter? While Wainwright's numbers this season improved considerably from 2005, when he was used exclusively as a starter, that should not come as a surprise. Baseball Prospectus research indicates that the typical pitcher can expect a 25% reduction in his ERA if he moves from the rotation to the pen; Wainwright saw his ERA drop from 4.40 in '05 (in Triple A, no less) to 3.12 this season.

Wainwright is not the only young, recently converted closer whose potential value as a starter has been hotly debated in recent months. In September the Red Sox announced that Jonathan Papelbon (35 saves, 0.92 ERA in '06--his first season as a full-time closer) would rejoin the rotation next season. Earlier this year, on BaseballProspectus.com, I argued that the Red Sox should not take Papelbon out of the closer role and identified two characteristics of pitchers who tend to do better in the bullpen: They are occasionally wild, due in part to imperfect mechanics, and they don't give up a lot of home runs. Like other successful starter-to-reliever converts such as Tom Gordon and J.J. Putz, Papelbon has those characteristics.

But the 25-year-old Wainwright is not that sort of pitcher. His command has always been his biggest strength, which suggests that his mechanics are stable enough to handle longer outings. And his reliance on the curveball--a pitch that can be hit a long way when it hangs in the strike zone--has led to periodic problems with the home run ball throughout his professional career. Wainwright should continue to serve St. Louis well as a closer, but he might be even more valuable to the team as a starter, a role in which his numbers and repertoire resemble those of the late Darryl Kile.