Mike Napoli hit a solo homerun with two outs in the ninth inning to give the Boston Red Sox a 2-1 win over their biggest rivals, the New York Yankees.
Napoli struck out in his previous two at-bats before smacking an opposite-field drive off Yankees pitcher Masahiro Tanaka on Saturday.
The victory was one of only three in the last nine games for the struggling Red Sox, who sit at 37-44 halfway through the season. It is the first time since 1997 that Boston has been under .500 at the midway mark.
Jon Lester (9-7) held the Yankees hitless until the sixth inning, while Tanaka (11-3), the American League's ERA leader, gave up seven hits in a complete game, striking out eight and walking one.
Elsewhere in AL action, the Oakland Athletics got a go-ahead run off a Josh Donaldson two-out single to beat the Miami Marlins 7-6, while Toronto fell 4-3 to the Chicago White Sox, who had lost 11 of their last 14 games.
The Rays beat the Orioles 5-4, and in another close game, a ninth-inning, three-run homer put the Detroit Tigers ahead of the Houston Astros, 4-3.
In National League play, the Los Angeles Dodgers dominated the St. Louis Cardinals, 9-1, while Arizona came out ahead, 3-1, over the San Diego Padres. Cincinnati beat San Fracisco 7-3.
The Washington Nationals swept two games against the Cubs, 3-0 and 7-2, respectively, while in the day's other doubleheader, the Atlanta Braves beat the Philadelphia Phillies 10-3 and 5-1.