Looking at the performance record, note the consistent disparity in innings pitched across the two splits. Overall, Wang has thrown 55 percent of his innings at home, suggesting that the Yanks may regard that setup as optimal. Second, while Wang's home/road split has been consistent across all three years, the actual ERA disparity is much, much wider than suggested by his peripherals, as reflected via FIP [Fielding Independent Pitching]; an apparent home-field advantage of 0.14 runs according to FIP turns into a 1.58 run advantage according to ERA. For those wise enough to pooh-pooh the earned/unearned run distinction, the spread is 1.82 runs per nine innings.Turning to the group of 65 pitchers (including Wang) who threw at least 50 innings at home and on the road in each of the last three seasons -- a group that's decidedly better than league average -- we see:
The difference appears to be largely due to the results of balls in play. Wang's BABIPs at home have consistently been about 40 points below the league averages (.296, .305, and .308, respectively, over the last three years), enabling him to beat his FIP estimates by 0.78 runs. On the road, his BABIPs have been about 15 points above, with a much wider variation from year to year; collectively, his road ERAs have been 0.66 runs higher than his FIPs.
This discrepancy could be random, but it may not be. Along with the ballpark-to-ballpark variations in fence distances and the amount of foul territory, home/road differences may be a reflection of field preparation. It's no secret that groundskeepers can prepare the field to the benefit of the home team's starting pitcher. For any pitcher, that may include tailoring the mound to his liking. For a groundballer, that may include watering down the area in front of home plate and leaving the infield grass longer; likewise, for an opposing groundballer, the crew may opt to cut the grass short and keep the plate area dry and hard. The TBS broadcast of Game Two of the Cubs-Diamondbacks series showed the Arizona crew watering down home plate before the game even as the umpires looked on. Lou Piniella complained, prompting the umps to order the application of a drying compound, but the results were still reportedly damp. Still, there's an element of tradition involved—such groundskeeping gamesmanship goes back to the 19th century, as teams even back then were watering down the basepaths to slow down their speedier opponents.
Home RoadMore detailed breakdowns can be found at the BP, where the piece is free. The take-home message is this:
GB 3.78 4.23
FB 4.16 4.45
What this in-no-way-definitive study suggests is that a groundballer pitching at home -- exactly like Wang in Yankee Stadium -- would appear to be the best of the limited permutations available. Further research along these avenues is needed to clarify the matter, but at River Avenue and 161st Street in the Bronx on Thursday night, with the Yankees' continued presence in the postseason and Joe Torre's tenure in pinstripes riding on Wang's performance, it will have to do.Go Yanks!
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