OAKLAND, Calif. -- One swing from Leonys Martin capped an impressive comeback by the Seattle Mariners.

Martin launched a tiebreaking home run with two outs in the top of the 10th inning, and Seattle held on for a 7-6 victory over the Oakland Athletics on Tuesday night at Oakland Coliseum.

The Mariners' No. 9 hitter belted reliever Josh Smith's 2-1 pitch into the right field seats for his second home run of the season, completing Seattle's rally from a 5-1 deficit after three innings.

"I put a good swing on it," Martin said. "I was seeing the ball really good tonight. I feel really confident. I didn't try to hit a homer. I was trying to put a good swing in."

Edwin Diaz pitched a scoreless 10th for his 24th save, stranding runners on first and second.

The Mariners moved into a three-way tie for the second American League wild-card spot with Kansas City and Tampa Bay.

"It wasn't easy, that's for sure," Mariners manager Scott Servais said. "Down early, we kept chipping away. A lot of good at-bats."

The Mariners saved their best at-bat for last, when Martin went deep for a second time since being recalled from Triple-A Tacoma on July 30.

"Obviously, I couldn't be happier for Leonys Martin," Servais said. "The last time we were in Oakland, we had to designate him to send him down. He's busted his butt down there the whole time in Triple-A. He's helped us out a ton since he's been back."

Khris Davis hit his 30th home run of the season for the A's, a three-run shot in the first inning. He had an RBI triple and scored in the second. Ryon Healy went 3-for-4 with his 21st home run in the fifth.

Ben Gamel went 2-for-5 with a double, two RBIs and a run for Seattle. Yonder Alonso went 1-for-5 in his Mariners debut, two days after he was acquired from the A's.

Oakland right-hander Kendall Graveman allowed four runs (three earned) and seven hits in 5 1/3 innings. He struck out two and walked one in his second start since being reinstated after spending more than two months on the disabled list with a strained right shoulder.

"I started out well," Graveman said. "I needed a quick out in the sixth. My stuff flattened out at the end, and they did a good job of putting it in play."

The A's used all seven of their relievers, including three in the seventh inning. Smith (2-1) took the loss. Oakland committed three errors and allowed two unearned runs.

"When you play close games like that, making three errors is certainly not going to help," A's manager Bob Melvin said. "We've got to get cleaner. You can't make three errors and expect to win."

Mariners left-hander Ariel Miranda gave up six runs and five hits, including two home runs, in five innings with six strikeouts and two walks. He has allowed 29 homers this season.

Seattle relievers Casey Lawrence, Nick Vincent, Marc Rzepczynski (2-0) and Diaz combined to blank the A's over the final five innings. Lawrence had four strikeouts in two innings.

The A's led 6-2 through five innings, but the Mariners scored twice in the sixth. Nelson Cruz and Kyle Seager hit back-to-back singles, and Gamel brought them home with a double.

The Mariners cut Oakland's lead to 6-5 in the seventh. Jean Segura singled and advanced to second on right fielder Matt Joyce's fielding error. Segura moved to third on Alonso's infield single and scored on Cruz's soft single.

Seattle pulled even with an unearned run in the eighth. Leading off, Gamel hit a ground ball to third baseman Matt Chapman, who airmailed his throw for a two-base error. Gamel scored from third on a sacrifice fly to shallow center field by pinch hitter Danny Valencia, beating Rajai Davis' throw.

"You've got to go for it," Servais said of third base coach Manny Acta sending Gamel. "We've got to be aggressive, all of our guys."

The Athletics struck quickly, taking a 3-0 lead in the first inning.

Rajai Davis lined a leadoff double off the left field fence, shortstop Marcus Semien walked, and Khris Davis launched an opposite-field home run down the right field line with one out.

Seattle cut Oakland's lead to 3-1 in the third inning with an unearned run.

Mike Zunino had a one-out infield single and went to second on Semien's throwing error. Zunino moved to third on Martin's single and scored when Segura grounded out.

Oakland made it 5-1 in the bottom half.

Healy lined a leadoff single and scored when Khris Davis launched a triple that bounced off the center field fence and past center fielder Jarrod Dyson. Davis scored on Chapman's sacrifice fly.

The Mariners scored a run in the fourth on Dyson's RBI single with two outs.

Healy increased Oakland's lead to 6-2 with a solo shot to left-center field in the fifth inning.

NOTES: Seattle RHP Felix Hernandez (right shoulder bursitis) is expected to miss three to four weeks. He underwent an MRI and was examined by team medical director E. Edward Khalfayan in Seattle on Monday. He was placed on the 10-day disabled list on Aug. 5, retroactive to Aug. 2. ... Seattle RHP David Phelps (right elbow impingement) was placed on the 10-day DL and is expected to miss two to three weeks. Phelps, a reliever, left the first game of Seattle's doubleheader against Kansas City on Sunday after facing only one batter in the seventh inning. ... RHP Ernesto Frieri was acquired by the Mariners from Texas for cash considerations and was assigned to Triple-A Tacoma. ... A's 1B/OF Matt Olson was recalled from Triple-A Nashville and began his sixth stint with Oakland this season. Olson, a left-handed hitter, is expected to platoon with 1B/3B Ryon Healy at first base, starting against right-handed pitchers. ... C Ryan Lavarnway was outrighted by the A's to Nashville three days after being designated for assignment.