SEATTLE -- The Oakland A's haven't had much to celebrate this season, so seeing shortstop Marcus Semien go deep in the 13th inning of Saturday night's game against Seattle was a welcome change.

Semien hit a two-run homer in the top of the 13th inning to give the A's the lead for good on the way to a 7-5 win over the Mariners.

Semien's fourth home run at Safeco Field this season came after a leadoff single from catcher Stephen Vogt as the A's (68-96) won their third game in a row for the first time since Aug. 29-31.

"We've had a lot of those extra-inning games that haven't gone our way this season," Semien said. "With one more game to go, it's nice to get that win like that."

Switch-pitcher Pat Venditte (2-2) posted the win after pitching three scoreless innings of relief. Oakland starter Felix Doubront came out of the bullpen in the bottom of the 13th to secure his first save in four years.

Seattle's JC Ramirez (1-2) took the loss after giving up Semien's homer.

The two teams combined to use 16 pitchers in a game that took four hours and 31 minutes to complete.

In terms of innings played, it was the longest game at Safeco Field this season and the longest one involving the Mariners. Seattle (75-86) has lost nine of its past 10 games.

Oakland jumped out to 4-0 lead in the top of the third inning before Seattle second baseman Robinson Cano hit a three-run homer to give the Mariners life. Seattle shortstop Ketel Marte drove in the go-ahead run with an RBI single in the sixth, giving the Mariners their first lead at 5-4.

The A's tied the score 5-5 on a sacrifice fly from second baseman Brett Lawrie in the ninth.

Seattle closer Tom Wilhelmsen blew a save for the second time in as many opportunities after opening the ninth with a walk, a hit batter and a wild pitch to put runners on second and third with no outs. Lawrie's fly to left scored leadoff hitter Billy Burns from third to tie the score.

"Tough," Mariners manager Lloyd McClendon said. "We had a chance to win and our closer's in there."

Oakland manager Bob Melvin said the A's were due for a win like this.

"The guys have persevered all year," he said. "A lot of these games this year, we've lost this type of game right here. We had to use an awful lot of guys and everybody contributed."

Oakland starter Sean Nolin allowed three runs and six hits in five innings in his sixth start since being promoted from Triple-A Nashville.

Nolin left with a 4-3 lead, but the Mariners took their first lead in the sixth. After the first three Seattle batters reached to load the bases with no outs, catcher Jesus Sucre hit into a double play that scored right fielder Mark Trumbo from third base for a 4-4 tie. One batter later, Marte put the Mariners ahead 5-4 with an RBI single up the middle.

Cano went 2-for-3 to extend his hitting streak to 15 games. Marte and outfielder Brad Miller each had two hits. Marte reached base four times, twice on errors and on a bunt single to lead off the ninth.

Oakland first baseman Mark Canha and second baseman Brett Lawrie each had two hits.

The A's had three errors, extending their American League-leading total to 125. Semien committed his 35th error, the most among any AL player.

Venditte retired all nine batters he faced to claim the win. He didn't have to go against Seattle slugger Nelson Cruz, who strained a groin in the ninth inning, forcing the Mariners to use backup catcher John Hicks as a pinch hitter in the 12th.

Asked whether Cruz would be held out of Sunday's season finale, McClendon said: "I would imagine so."

Venditte logged his second win of the season and saw his season ERA drop to 4.40. He didn't mind playing in one of the longest games of the season on a night when both teams were playing with nothing on the line.

"You're talking to a guy who was in the minor leagues for seven years, so just being able to play in the big leagues, every day is perfect as long as I get to play here," he said. "That's how the whole team thinks. No matter where we are in the standings, we've got a job to do and we're glad to do it."

Three-run homers by Oakland third baseman Danny Valencia and Cano created some early fireworks.

Valencia went deep for the second time in as many at-bats with his first-inning shot. Valencia, who hit the winning homer in his final at-bat of Friday's game, gave Oakland a 3-0 lead with his 18th homer of the season. An RBI from Vogt in the top of the third allowed the Athletics to open a 4-0 lead.

Cano responded with a three-run blast in the bottom of the inning for his 21st home run of the season.

Seattle starter Roenis Elias never found a rhythm and was taken out after two third-inning walks loaded the bases. In two innings, Elias threw 51 pitches while allowing four runs, seven hits and three walks.

Oakland had three errors in the first five innings, giving it a major league-high 125 for the season. Semien had a fifth-inning error, giving him 35 this season -- by far the most in the American League.

NOTES: The San Francisco Chronicle reported Saturday that LHP Drew Pomeranz might have to undergo arthroscopic surgery. Pomeranz has struggled with soreness in his AC joint on several occasions this season and was shut down for the final week. ... Mariners RHP Carson Smith tied the team record for strikeouts in a season by a rookie reliever. Smith matched Enrique Romo's 38-year-old record of 92 strikeouts. ... Seattle 2B Robinson Cano has a 15-game hitting streak - the longest active one in the majors. ... Mariners DH Nelson Cruz has 44 home runs, second in the American League behind Baltimore's Chris Davis (45). Because of his groin injury, he's likely to fall short of his quest to be the first AL player since Jose Bautista in 2010-11 to win the league's home run title in back-to-back years.