"There's another unintended consequence that could occur in 2013 when the Astros move to the American League; with 15 teams in each league it will be necessary to have interleague play all season, instead of having it shoved into one block in June...Baseball's schedulers might be able to work out a scheme where no one plays more than 18 interleague games (the current maximum), but another workable schedule would have teams playing as many as 30."

Can someone please explain this to me? Why does interleague scheduling have to be radically changed due to balanced leagues?