Thursday, March 12, 2009

WBC Starting Pitchers Likely to Suffer Early Season Woes

Evidence from 2006 data shows that starting pitchers who play in the World Baseball Classic are likely to suffer decreased performance in the first month of the season as a result of pitching in the WBC.

The study done at Behind the Scoreboard (full technical version here) focused on 22 starting pitchers who both pitched for their country and saw significant major league action in 2006, the last time the WBC was held. The study's hypothesis was that due to poor preparation, starting pitchers would perform worse during April versus the mid-season months of May-August. The data showed with statistical significance that indeed the WBC pitchers performed worse during April than the rest of the year. On average the WBC pitchers had an increased ERA of 0.67 points during the first month of the season.

The study was carried out by taking the difference between each pitcher's April and mid-season ERAs and giving each player a weight based on the number of innings pitched in each period. The weighted average of all players showed that WBC pitchers could expect an April ERA boost of 0.67 points over their usual ERA. The standard deviation of the estimate was 0.43, making the increase in ERA a statistically significant result.

The result gives further evidence to back up anecdotal theories on how the WBC robs pitchers of essential preparation time needed to get ready for the beginning of the season.

The study also examined whether starting pitchers' September performance suffered due to fatigue from starting their season early, but found no such evidence. Hitters and relief pitchers were also examined for both early and late season dropoffs in performance due to WBC participation, but no statistically significant results were found.