BOSTON (AP) -- A five-run lead wasn't enough to save Baltimore from a series of late defensive blunders.
A hanging curveball, a wild pitch and three errors in the final three innings ate away at the Orioles' lead as the Boston Red Sox rallied for a 6-5 victory Sunday night.
"That was the difference in the game," Baltimore manager Buck Showalter said.
The defensive breakdown ended on left fielder David Lough's throwing error that allowed Dustin Pedroia score after tagging up on a line drive.
Jonny Gomes hit a three-run homer for the Red Sox in the sixth, then Boston tied it with two runs in the seventh after Baltimore bobbled away a chance for a double play that would have ended the inning.
Ryan Flaherty, who started the game at third but moved over to shortstop when J.J. Hardy left in the top of the inning with a strained right hamstring, dropped the ball while transferring it from his glove to his hand for a throw to first.
"That's the way the rule is. I didn't turn the double play like I should have," Flaherty said. "We didn't make plays on defense like we should have. That's what happens when you give a good team extra outs."
Adam Jones had three singles and a double, and Nelson Cruz hit a solo homer to spark a three-run first inning for the Orioles.
Boston can take three of four when the series concludes with Monday's traditional 11 a.m. Patriots' Day start.
Dustin Pedroia opened the ninth with a replay-reviewed double off the top of the Green Monster against Brian Matusz (1-1). With the crowd chanting "Home Run! Home Run!" The ruling was the "call stands" after a 2-minute, 2-second delay. A fan had reached over just at the line at the top of the wall to touch the ball, and replays appeared inconclusive.
Pedroia advanced on a wild pitch and, after David Ortiz was intentionally walked, Darren O'Day hit Mike Napoli on the left knee to load the bases. Pinch hitter Mike Carp hit a liner to left. Pedroia tagged and broke down the line, but headed back. Lough's throw was wide of the plate and bounced around as Pedroia raced home.
Orioles manager Buck Showalter and a few players had a lengthy discussion with the umpiring crew before the teams left the field.
Edward Mujica (1-1) got one out for the win.
"It's frustrating," Flaherty said. "We had a chance to win the game and didn't."
Baltimore had built a 5-0 lead in the sixth against Boston starter Jake Peavy, who was roughed up for 10 hits in 5 2-3 innings.
Ubaldo Jimenez had his best start since signing a big free agent contract with Baltimore, pitching five shutout innings before being chased on Gomes' three-run homer in the sixth.
The Red Sox then tied it against reliever Zach Britton in the seventh. Ortiz's RBI single cut it to 5-4 before Jonathan Schoop, who moved from second to third that inning, bounced a throw home for an error attempting a force at the plate on a bases-loaded grounder.
Jimenez, who signed to a $50-million, four-year deal, had allowed at least four runs in each of his first three starts. He gave up three on four hits, walked three and fanned five.
Peavy had held opponents to two or fewer runs in all of his first three starts.
Cruz, the second batter, hit the first pitch into the seats above the Green Monster. Matt Wieters had an RBI single and Hardy added a sacrifice fly.
Lough's RBI double made it 4-0 in the fifth and Jones' run-scoring single chased Peavy.
Jimenez, who entered 1-3 with a 10.27 ERA in five career starts versus Boston, held the Red Sox hitless until Gomes' two-out double in the fourth.
NOTES: RHP Clay Buchholz (0-1, 5.51 ERA) goes for the Red Sox against LHP Wei-Yin Chen (2-1, 4.76) on Monday. ... Showalter said he'd like to keep playing Schoop at second and third until 3B Manny Machado returns from extended spring training, where he is working back from offseason left knee surgery. "I don't want him to get too far away from second," Showalter said. "I want him to play some over there. When Manny comes back he might be over there." ... Boston manager John Farrell said he expects 3B Will Middlebrooks, on the 15-day DL with a strained right calf since April 6, to begin a rehab assignment with Triple-A Pawtucket this week. Middlebrooks said he was "feeling great" before the game.