If not for interleague play, the AL races would be vastly different this year. The RedSawx feasted on the leasts from the (NL) East, The Chisax and Twins ripped their NL foes; the Yanks, Angels, A's and Rangers all scuffled. Consider these AL-only records:
Without interleague play, the Tigers are still rolling toward a division crown, but the Palehos have a 2-game wild card lead over the Angels (who are now 9 out), and 2.5 over the Redsux and Twinkies, with the Rangers and BloJs in the mix. The Yanks would be rocking toward a ninth-straight divisional title with an 8-game lead over the Redstiffs. There is really no way to understate this: the AL's dominance of interleague play has had a huge impact on the AL races because those teams that did not dominate their inferior foes in the NL lost opportunities (and ground) to capitalize on their weak schedules. The Twins (16-2), Palehos (14-4), Tigers (15-3) and Redsux (16-2) treated their NL foes like so many different versions of the Royals and that is the sole reason the RedSux are even in the AL East race at all.
Indeed, this year interleague play may have the largest effect on the playoff participants since its inaugural season of 1997 -- that year the Marlins had the best record against AL teams, the Mess were mediocre, the Marlins won the wild card over the Mess (and others) and ultimately won the World Series.
Does this mean anything going forward? The Monk doesn't know. It seems that A's, Tigers, Palehos and (yes) Yankees fans can take some miniscule comfort from the fact that their teams are the four-best against AL opponents and therefore have done the best against the better league. This is important because no more interleague games exist until the World Series. But in baseball (even more than in investing), past performance is no indicator of future success. Thus, the Redstanx and Twinkies should be thanking Commissioner Selig for his "invention" whilst the Angels and BlooJs grumble.