"I was a little nervous when he threw it that I was going to be out at third, so there was a lot going on," Pedroia said. "All their outfielders have great arms, so you have to get a great jump for situations like that. We just lucked out."
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 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, setting off the game-ending play.
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.
"He was going in circles," Carp said of Pedroia's route. "He was running around. The only thing that matters is we got the win."
Jonny Gomes hit a three-run homer for the Red Sox, who overcame a 5-0 deficit.
It was an emotional win on a night when the Red Sox had a moving pregame ceremony for victims of Boston Marathon bombings before the game. Just over a year ago, three were killed and over 260 injured when two bombs went off near the finish line.
"I think it really sunk in how much it's been a year down the road," Gomes said.
The ceremony also honored first responders, runners and volunteers of the marathon. The family of Lu Lingzi, a Boston University graduate student from China that was killed in the bombings, made their first ever visit to Fenway Park and closed the ceremony with the traditional "Play Ball!" chant before the Red Sox took the field.
Adam Jones had three singles and a double, and Nelson Cruz hit a solo homer to spark a three-run first for the Orioles.
Boston can take three of four when the series concludes with Monday's traditional 11 a.m. Patriots' Day start.
Orioles manager Buck Showalter and a few players had a lengthy discussion with the umpiring crew before the teams left the field.
"They've got some really strange things you can't appeal," Showalter said of the play, saying he was wondering if all the runners had tagged. "David made a heck of a play there at the end, just threw it a little wildly."
The Orioles had a runner on third with one out in the ninth, but Andrew Miller got one out and Mujica fanned Lough.
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. It allowed the tying run to score. Shortstop Ryan Flaherty, who started the game at third but moved over when J.J. Hardy left in the top of the inning with a strained right hamstring, dropped a throw at second for an error on an attempted force.
"I dropped the ball. Didn't turn the double play like I should have," Flaherty said. "That's the way the rule is. I didn't turn the double play like I should have."
Jimenez, who signed to a $50-million, 4-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 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.