The American League leads the National so far in this year’s interleague play. That isn’t especially noteworthy, given that the AL has held the advantage in interleague play for six consecutive seasons coming into this one. But there are a few details about this year’s interleague competition that might indicate that the AL’s stranglehold over the NL is weakening—or they might not.
There’s still a week of 2011 interleague play remaining, but the count as of the completion of yesterday’s games was American League 88 wins, National League 80. That calculates as a winning percentage of .524.
A winning margin of .524 in a sample of this size is convincing, but hardly dominating. If this margin holds, though it would be the seventh straight year of AL superiority, it would be the closest margin of any of the seven years. The second-closest margin? Last year’s, at .532.
This would seem to suggest that, although the Junior Circuit retains its demonstrated advantage in quality of play, the gap is narrowing. And if that’s the case, if the trend continues, the NL will catch up shortly.
However, there is another detail that leads one to hesitate to reach that conclusion, and that is the Pythagorean record of interleague play. In 2010, the Pythag of the accumulated scores of all interleague games was exactly equal to the actual won-lost record: the AL’s Pythag was .532. But so far in 2011, though the margin of AL superiority in actual wins and losses is down to .524, the Pythagorean record at this point is in the AL’s favor to the tune of .561.
Pythag records are worth noting because they often serve as more reliable predictors of future performance than actual won-lost records. If that proves to be the case here, the “closing the gap” indication would be something of an illusion.