2011 Interleague play:  Same old, not-so-same old?

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.

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Comments

  1. Jim Bouldin said...

    “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.”

    Maybe.  But it indicates that the NL has gotten increasingly good at winning the tight games—which would not surprise me if this were true.

    That is, when the AL gets a big lead, the NL teams just don’t have the firepower to catch up, usually.  But when games are close, the NL hangs in and wins more than its share.  Thus a high Pythag for the AL relative to actual W:L ratio.

    If the NL teams can reduce the number of big early deficits, this bodes well for them to start winning more than the AL.

  2. Steve Treder said...

    Well, possibly.  But the NL demonstrated no particular capacity to win the close ones last year, when the Pythag and the actual W-L were identical.

  3. Jim Bouldin said...

    “Well, possibly.  But the NL demonstrated no particular capacity to win the close ones last year, when the Pythag and the actual W-L were identical.”

    Right—that’s what you would expect when the Pythag equals the actual.  But when the Pythag exceeds the actual (as it now does for the AL this year), this means the NL is winning the closer games.

  4. Steve Treder said...

    By defintion it means the NL is winning the closer games in 2011.  My point is that I’m skeptical that this is a repeatable skill that the NL has suddenly gained this year.  More likely, I would say, the deviation from Pythag in 2011 is a random variation.

  5. Jim Bouldin said...

    “By defintion it means the NL is winning the closer games in 2011.  My point is that I’m skeptical that this is a repeatable skill that the NL has suddenly gained this year.  More likely, I would say, the deviation from Pythag in 2011 is a random variation.”

    Tough call on that.  One could look at the last few years to see if there’s any trend.

  6. hk said...

    Last night’s 4 NL wins to 2 for the AL takes the AL’s winning percentage down to .517.  What did last night’s cumulative 34-13 run differential do to the pythag record?

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