Oakland starter Jacob Lopez matched the effort, allowing two runs on seven hits over 5 1/3 innings with eight strikeouts.
Boston responded with a solo home run by Jahmai Jones in the fifth inning and an RBI single from Sacramento native Nick Sogard in the sixth to tie the game at 2-2.
Sogard was recalled from Triple-A Worcester earlier in the day to replace Curtis Mead, who suffered a fractured wrist on Monday.
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In the first inning, Athletics slugger Nick Kurtz was forced to exit after being struck on the left forearm by a 95 mph sinker from Sandoval, marking the second time in the series a player was injured by a pitch.
