Following the Phillies’ spanking at the hands of the Red Sox on Wednesday, the club is 2-4 in interleague contests this season. With matchups against the Angels, A’s and Rangers—but not the cellar-dwelling Mariners—on tap for the next nine games, things might not improve very much. Joe Sheehan of Baseball Prospectus had a great column on Monday describing how the unbalanced interleague schedule distorts the playoff races, including a note that the two games by which the 2001 Phillies fell short of the Braves for the NL East championship was covered by the difference in the teams’ interleague records. Interleague made the difference for the Phils' playoff hopes five years later as well. In 2006, the Phillies missed the wild card by three games as the Padres and Dodgers both made the playoffs with identical 88-74 records; the Phils went 5-13 in interleague that year, while San Diego went 7-8, 3.5 games better.
But I have to admit that it’s really the team’s awful interleague record over the 12 seasons since Bud Selig decided this would be fun that drives my disdain. Through yesterday, the Phillies are 88-102 against AL opponents, for a winning percentage of .463. That's tied with the Brewers for 12th of the 16 NL clubs, better than only the Pirates, Reds and Padres. (See here for 1997-2007 interleague records.)
Overall since 1997, the Phillies are 927-928 (.4997, or .500). In NL-only games since then, they’re 839-826 (.504). I suspect the revenue boost from hosting the Red Sox and Yankees probably makes the novelty more appealing to the team's ownership, but for competitive purposes, it's been a lemon.