Khris Davis hit a tiebreaking, three-run homer off David Price with two outs in the eighth inning and the Oakland Athletics beat the Boston Red Sox 4-1 on Sunday.
A day after getting no-hit by Sean Manaea, Boston lost back-to-back games for the first time under new manager Alex Cora.
The Red Sox had won their first six series this season before dropping two of three at the Coliseum. They still have the best record in the majors at 17-4.
Davis had two hits and drove in all four runs for the A's. Marcus Semien and Stephen Piscotty added two hits apiece as Oakland won for the sixth time in seven games.
Semien and Piscotty hit back-to-back singles off Price (2-2) with one out in the eighth. After Jed Lowrie struck out for the third time, Davis lined the first pitch into the seats in left field for his sixth home run.
Davis also had an RBI single off Price in the first.
Price allowed nine hits and four runs over 7 2/3 innings. He struck out six and walked one.
Coming off Manaea's gem, the A's got another strong pitching performance against the hard-hitting Red Sox. Daniel Mengden gave up one run in 6 1/3 innings and Blake Treinen (1-1), Oakland's third reliever, retired five batters to win.
Treinen appeared to injure his left ankle while fielding Blake Swinhart's comebacker but remained in the game and got Christian Vazquez to fly out to end it.
Mitch Moreland had two hits and Brock Holt drove in Boston's lone run.
Mengden allowed a pair of first-inning singles, then retired 16 of 17 before yielding back-to-back hits in the seventh. He left after giving up Holt's tying RBI double in the seventh.
Red Sox: LHP Bobby Poyner was activated off the disabled list and optioned to Triple-A Pawtucket. He had been out with a left hamstring strain.
Red Sox: RHP Rick Porcello (4-0, 1.40) pitches the opener of a three-game series in Toronto on Tuesday. He has thrown 13 consecutive scoreless innings over his previous two starts.
Athletics: RHP Trevor Cahill (1-0, 0.00) makes his second start of the season Monday at Texas. It's the first time this season that the A's will leave the West Coast.