Wacha allowed just two earned runs in six innings in Game 2. Reuters

Jon Jay scored the go-ahead run on an error during a three-run seventh inning as the visiting St. Louis Cardinals evened the World Series at a game apiece against the Boston Red Sox at Fenway Park, 4-2.

Michael Wacha (1-0) allowed two runs on three hits in six innings and Carlos Martinez struck out three in two scoreless frames before Trevor Rosenthal struck out the side in the ninth on 11 pitches for the save. Carlos Beltran started despite suffering a rib contusion in Game 1 and contributed two hits and an RBI while Matt Carpenter plated the tying run for the Cardinals, who host Game 3 on Saturday.

David Ortiz hit a two-run homer and John Lackey (0-1) worked six strong innings before running into trouble and being charged with three runs on five hits. Craig Breslow allowed two inherited runners to score and yielded an unearned run of his own in the seventh while recording just one out as the Red Sox had a nine-game World Series winning streak come to an end.

Lackey issued a one-out walk and allowed a weak single in the seventh before being replaced by Breslow, who walked Daniel Descalso to load the bases. Carpenter followed with a short fly to left, and pinch runner Pete Kozma scored as the throw got away from catcher Jarrod Saltalamacchia.

Breslow retrieved the errant throw and fired to third, sailing it over Stephen Drew’s head and into the box seats up the left-field line to allow Jay to cross the plate with the go-ahead run. Carlos Beltran’s RBI single made it a 4-2 advantage.