OAKLAND, Calif. -- Khris Davis summed up his deciding home run off Boston lefty David Price in less time than it took for the ball to clear the fence.
"First pitch hacking," Davis said. "That's what happened."
Davis hit a tiebreaking, three-run homer with two outs in the eighth inning, sending the Oakland Athletics over the 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.
"Our pitching staff will always give us a chance to win. I feel we are capable of scoring runs every night. Obviously, that's not always going to happen. We can't score eight or nine runs every night," Cora said.
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.
"It's big knowing we can compete with good teams like Boston," Davis said. "We just have to ride the wave out as long as we can. The pitching has been fantastic. Any time the pitching is on, we want to be putting up runs."
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.
"Got a good pitch to hit and he hammered it," A's manager Bob Melvin said. "He's a three-run homer waiting to happen."
Davis also had an RBI single off Price in the first.
"He's very lethal," Semien said of Davis. "He got a pitch he could handle and he didn't wait around. He's hit so many home runs here. That was one of his biggest ones."
Price allowed nine hits and four runs over 7 2/3 innings. He struck out six and walked one.
"I couldn't make the pitch when I needed and that was the ballgame," Price said.
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.
Treinen tweaked his left knee while fielding Blake Swihart'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.
CHANGING IT UP
Mengden allowed a pair of first-inning singles, then retired 16 of 17 before yielding back-to-back hits in the seventh. The right-hander with the handlebar mustache credited a new reliance on his changeup for the success.
"I probably threw the most changeups I've ever thrown in my life," Mengden said.
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.