Jarrod Saltalamacchia's two-run homer in the bottom of the ninth sent the Fenway faithful into a frenzy Tuesday night as Boston tied the game 6-6 and headed to extra innings.
Baltimore, however, had enough of the excitement as Ronny Paulino and Endy Chavez drove in runs in the 10th inning and Baltimore escaped with an 8-6 victory.
Alfredo Aceves took the loss for Boston.
Tuesday's starter, Jon Lester, allowed two earned runs on eight hits in six innings.
Mike Aviles had three hits for Boston in the loss.