Anaheim, Calif. ? Jason Bay hit a go-ahead, two-run homer off John Lackey in the sixth inning, and the World Series champion Boston Red Sox beat the Los Angeles Angels, 4-1, on Wednesday night in the opener of their AL playoff series.

Acquired in the three-team trade that sent Manny Ramirez to the Los Angeles Dodgers, Bay brought Boston back from a 1-0 deficit in the first postseason game of his career, and the Red Sox got a big start from John Lester (1-0), who allowed only an unearned run in seven innings.

“It’s big. Any time you can come into another team’s ballpark and win is huge,” Lester said.