Interleague play, now in its 11th year, is back this weekend with some great natural rivalries such as the Mets-Yankees, Cubs-White Sox, A's-Giants, Angels-Dodgers, and, of course, Rockies-Royals and Phillies-Blue Jays. OK, not all the rivalries are great, or natural.

Despite its critics, interleague play is here to stay. Why? Because it makes money.

Average attendance for interleague games last year was 34,097 compared with 31,112 for league games. In the first 10 years of interleague play, average attendance for interleague games was 32,842. League games over that span averaged 29,211.