Carlos Zambrano recently received his third Silver Slugger award, and second straight, as the best hitting pitcher in the National League. Zambrano actually dropped off considerably in his offensive production in 2009, seeing his OPS drop from .892 to .689.
But that .689 is nearly double the league average pitcher; National League hurlers compiled a miserable .355 OPS in 2009.
Given that Zambrano represents such a remarkable upgrade from a normal pitcher, perhaps he can make a serious impact, even in such obviously limited offensive playing time (he accrued only 72 PA in 2009, and his career high is just 86).
Let's test the data. Zambrano had an OPS 94 percent above league average for pitchers. No other National League player did as well, relative to his position. But for the sake of an instructive comparison, let's assume that Zambrano is the equivalent, in the hitting pitcher community, to Albert Pujols. Pujols had an OPS 88 percent better than the overall league average, so the parallel is fairly drawn.
In exactly 700 plate appearances in 2009, Pujols added 69.7 runs to the Cardinals' ledger with his superior bat. Dividing that number by just under ten, to find Zambrano's contribution in 72 plate appearances, we get 7.17 runs added by Zambrano's bat.
Unfortunately, it isn't as simple as that, and the method I have just employed overstates the value of a good hitter on the mound. The reason is that the runs above average metric derives from a run-expectancy framework. This overestimates Zambrano's value by removing the context in which he performed from the equation.
For all position players, that is precisely what we want to do. But with pitchers, certain key variables enter the equation: first, managers nearly always remove pitchers who come to bat after the sixth inning with any men on base; second, pitchers who come to bat with runners on are generally expected to bunt; and third, pitchers bat less often with runners on base, because of the lesser quality of the hitters in front of them. Zambrano, therefore, is worth about ten percent less than that metric would indicate as a batter, because that is how much less than Pujols' his plate appearances were each worth.
Taking ten percent from 7.17 leaves us with only 6.46 runs of added offense, even though Zambrano so dominated his position offensively. In 2008, when Zambrano's OPS was 152 percent better than the league-average pitcher, he may have earned the cubs one extra win (generally, ten marginal runs equal a marginal win).
But in 2009, despite a second straight season with four home runs and a reputation as a slugger, Zambrano failed to change the Cubs' fortunes by even one game in the standings. He deserved the Silver Slugger. But instead of to pitchers, the Silver Slugger should probably go to a star pinch-hitter in the National League. That way, the award can reward more legitimate contributions to team success in run scoring.