Interleague play:  A change in the tide?

We’ve just wrapped up the first weekend of interleague play for 2010. And here’s the interesting news about that: National League teams got the better of it, albeit slightly, by a 22-20 margin.

Why might such an apparently inconclusive factoid be significant? Because, of course, the American League has routinely wiped the floor with the NL during interleague play over the past several years.

Interleague play debuted in 1997. Through the first eight seasons of this competition, the two leagues came out roughly even, with the National League holding a modest .507 advantage. But beginning in 2005, the AL suddenly and surely assumed top dog status, consistently and thoroughly drubbing their NL counterparts: from 2005 through 2008, the American League’s winning percentage in interleague play was a dramatic .571. In 2009, the NL was able to narrow the gap a bit, but the AL still came away with a convincing .548 advantage.

Thus these early 2010 returns, while obviously being subject to all appropriate Small Sample Size Alerts, are notable in how they DON’T resemble the results of the past five seasons.

Of course, this could be nothing, and the AL could continue to dominate interleague play over the rest of this year, and beyond. But perhaps not. The results of this weekend’s play suggest that it’s something that bears particular watching.

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  1. Mike Fast said...

    Small sample size caveats are definitely warranted.

    A whole season’s inter-league sample size is pretty small, enough that one standard deviation is something like 8-9 wins, iirc.

  2. Jim C said...

    A lot of the matchups favored the NL teams, like Baltimore at Washington, Rockies-Royals, and others. Also, perennial punching bag Pittsburgh sat this one out, playing the Braves.

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