BALTIMORE -- The Baltimore Orioles definitely do not consider themselves out of the wild-card chase. They sent that message once again on Tuesday night.

Chris Davis lined a walk-off single in the bottom of the 13th inning that gave the Baltimore Orioles a 6-5 victory over the Boston Red Sox.

The Orioles (71-73) crept back to within 5 1/2 games of the second wild-card spot with 18 games left. They've now won six of their last seven games in an attempt to keep those postseason hopes alive.

"I think after that long slide that we had where we just couldn't seem to put anything together or do anything right, I think a couple of the wins we've had here lately against the teams that we've been playing have kind of rejuvenated the team," Davis said. "We've been playing well."

Davis is a big reason for that. He went 2-for-6 with that one RBI and now has hit safely in 12 of his last 13 games -- batting .413 in that stretch. Power's been his calling card but the single in the 13th gave the Orioles what they needed on this night.

Right fielder Gerardo Parra started the game-winning rally with a walk off Red Sox right-hander Jonathan Aro. Third baseman Manny Machado then lined a single to center, and Parra never hesitated, easily making it to third.

Left-hander Robbie Ross Jr. then came on to face first baseman Davis. On a 2-1 pitch, Davis lined his game-winning single to right, bringing in Parra to end the 4-hour, 20-minute marathon.

Right-hander Chaz Roe (3-2) earned the victory after blanking Boston (68-76) in the 13th. Aro (0-1), who came on in the 11th, took his first major league loss for the Red Sox.

The Baltimore bullpen came through again, giving up just one run on six hits in eight innings, something that made manager Buck Showalter happy.

"We still feel like it's there for us if we can get the moment needed," he said. "It starts with good pitching, which we had tonight with the exception of ... one inning."

Boston had tied the game at 5-5 when first baseman Travis Shaw led off the eighth with a home run of left-hander Brian Matusz.

The Red Sox rallied from an early 4-1 deficit to force extra innings, and their bullpen might have been even better, holding Baltimore to just two runs on four hits in 9 2/3 innings thanks to a strong effort from eight pitchers.

"One after another, they stepped up and did their job," Red Sox interim manager Torey Lovullo said. "It was just a great effort all the way around. I couldn't be more proud of those guys."

The bullpen needed to step up because starter Joe Kelly came out after just 2 1/3 innings due to tightness and fatigue in the shoulder. The right-hander was trying to win for the ninth consecutive start, but Lovullo said they will re-evaluate the situation Wednesday and hinted that the team could shut him down.

"When they took me out, I was frustrated, obviously," Kelly said. "I wanted to stay in that game as long as I could. But the shoulder and the arm just wouldn't let me. ... It was just super tight."

Orioles starter Ubaldo Jimenez was trying for his 100th career victory, but the right-hander struggled with his command again and lasted just five innings.

He left with a 5-4 lead thanks to Machado's solo homer in the fifth, but first baseman Travis Shaw erased that with his lead-off homer in the eighth off left-hander Brian Matusz.

The Red Sox started the back-and-forth game when they took a 1-0 lead in the third on Shaw's bases-loaded walk.

The Orioles answered with four runs in the bottom half. Pearce started things with a two-run homer to left. Davis added a single but Betts' relay throw got loose on the Boston infield. That error let Machado score from third.

Kelly left after giving up a single to center fielder Adam Jones. Davis then scored when catcher Matt Wieters greeted left-hander Craig Breslow with a sacrifice fly that gave the Orioles a 4-1 lead.

The Red Sox then tied it with three off Jimenez in the fifth. Their first three batters got hits, the last being an RBI single from shortstop Xander Bogaerts. Designated hitter David Ortiz followed with a sacrifice fly.

That cut the lead to 4-3 before third baseman Pablo Sandoval later added an RBI single.

Sandoval initially was ruled safe at second before Buck Showalter challenged it, and the play got overturned for the inning's final out. Pearce made a good throw to second to nail Sandoval.

Machado then lined his tie-breaking homer in the fifth that stood up for three innings before the game went to extra innings.

NOTES: The Orioles recalled RHP Tyler Wilson, RHP Oliver Drake, INF Christian Walker and OF Junior Lake from Triple-A Norfolk on Tuesday. All four have played with the Orioles at various points this season. ... Orioles manager Buck Showalter said Norfolk manager Ron Johnson and pitching coach Mike Griffin will join the team starting with Monday's series in Washington. Norfolk was just eliminated from the International League playoffs on Monday night. ... Boston interim manager Torey Lovullo said 2B Dustin Pedroia will be in the starting lineup for the final two games of the series. The Red Sox gave him a break Monday to be careful with his hamstring, which kept him out for 42 games before returning Sept. 8. ... The series, which ends Wednesday, is the Red Sox's final visit to Camden Yards this year. The teams meet once more in Boston on Sept. 25-27.