BOSTON — Seattle's Raul Ibanez was fairly confident he was going to be racing home trying to score the go-ahead run. Instead, he could only watch as he was part of an unusual inning-ending unassisted double play.

A half-inning later, Stephen Drew singled in the winning run in the 15th to lift the Boston Red Sox to a 5-4 victory over the Mariners and back into first place in the AL East in a game that ended early Thursday morning.

Before Boston's 10th game-ending hit of the season, the Mariners had first and second with one out in the top of the 15th.

Ibanez and Endy Chavez had consecutive one-out singles. Michael Saunders then hit a low liner to left. Jonny Gomes charged in and made a diving, backhanded catch, then ran all the way to touch second base for the double play as Ibanez was standing near the third-base bag.

"My thought was freeze on a line drive, but my thought was based on where he was playing and the trajectory of the ball," Ibanez said. "I was sure off a left-handed hitter against a left-handed pitcher that it would fade and it did. He made a great play."

Seattle acting manager Robby Thompson didn't fault Ibanez for looking to score.

"(Gomes) was aggressive and made a good play on it and fooled Raul a little," Thompson said. "He was aggressive too, but that's OK."

The 17-year veteran Ibanez was surprised Gomes made the play.

"I saw where they were playing and based on the trajectory on Saunders' ball, I knew there'd be a little fade on it," he said. "I wasn't certain, but I did think that thing was going to bounce."

The Mariners left two runners on in the 11th and 12th, too. Thompson said he was encouraged by his team's effort.

"Once everyone got in, (I) just walked through (the clubhouse) and said 'Way to battle,'" he said. "It was a tough battle. It's hard to win on the road. They battled right to the end."

Dustin Pedroia drew a leadoff walk to start the bottom of the 15th and took second on a groundout by David Ortiz. Mike Napoli was walked intentionally and Jarrod Saltalamacchia struck out. Gomes then walked, loading the bases, and Drew hit a liner just inside the right-field line as Pedroia scored the decisive run.

Boston moved a half-game ahead of Tampa Bay in the division. The Rays lost 7-0 Wednesday night to the Arizona Diamondbacks.

Drew Britton (1-0) pitched two innings for his first major league win. Lucas Luetge (0-2) took the loss.

Boston wasted an excellent chance in the 14th when Brandon Snyder led off with a pinch-hit double, its first hit since the seventh, and took third on a sacrifice by Jacoby Ellsbury. But Snyder was thrown out trying to score on Shane Victorino's fly to center fielder Saunders, ending the inning.

Boston's previous longest game this year lasted 14 innings, a 10-8 win over Tampa Bay on June 10. Five days earlier, Seattle played its longest game, a 7-5 loss to the Chicago White Sox in 16 innings.

Kyle Seager had tied the game at 4 in the eighth with his 17th homer of the year, a solo shot off Junichi Tazawa.

Pedroia had given the Red Sox a 4-3 lead with a two-run homer in the seventh, his eighth, after a single by Victorino.

The Mariners went ahead 1-0 in the fourth on a run-scoring double by Seager before the Red Sox took the lead with two unearned runs in the fifth.

Brock Holt led off with a double and took third when center fielder Dustin Ackley dropped Ellsbury's low liner for an error. Victorino then grounded to second baseman Nick Franklin, who may have been distracted when Ellsbury ran in front of him.

Franklin bobbled the ball for another error as Holt scored. Pedroia then grounded into a forceout at second base, allowing Ellsbury to score.

The Mariners took a 3-2 lead with two runs in the sixth. They loaded the bases on a single by Humberto Quintero, a walk to Brad Miller and a single by Seager. Kendry Morales tied it with a sacrifice fly and Ibanez put Seattle on top with an RBI single.

Boston starter John Lackey shook off a liner off his left heel by Ackley in the third. Manager John Farrell and a trainer went toward the mound, but Lackey waved them away before they arrived.

Seattle starter Hisashi Iwakuma overcame a shaky start when he gave up singles to the first three batters in the first — Ellsbury, Victorino and Pedroia. But Ortiz grounded to Iwakuma, who threw home to start a double play, and the Red Sox didn't score. Iwakuma allowed just four hits in his remaining 4 2-3 innings.

NOTES: Seager went 3 for 6 and hit .396 in July (38 for 96). ... Lackey allowed at least three runs for the third straight game after giving up two or less in six consecutive starts. ... Iwakuma gave up no earned runs for his second straight outing. ... The Red Sox recalled Holt from Triple-A Pawtucket. He started in place of Jose Iglesias, who went to the Detroit Tigers on Tuesday night in a three-team, seven-player trade that brought RHP Jack Peavy to Boston. Peavy is expected to join the Red Sox on Thursday and pitch during the seven-game homestand that ends Sunday. ... Felix Hernandez (11-4) pitches for Seattle in the final of the three-game series against Ryan Dempster (6-8).