OAKLAND, Calif. -- Danny Valencia and Yonder Alonso spent the 2016 season as teammates with the Oakland Athletics.

On Tuesday night at the Oakland Coliseum, Valencia and Alonso teamed up to power the Seattle Mariners to a 6-3 victory against the A's.

Valencia hit a three-run homer, Alonso launched a two-run shot, and the Mariners defeated the A's for a franchise-record eighth straight time.

"It's pretty cool," Valencia said "We were talking about it. It's always nice to be in the lineup with him. I've been playing with him since high school (in south Florida). To come back here, both of us come back here, playing against our former team and do well and help the team win, it feels good."

Alonso hit his 27th home run of the season in the fourth inning, and Valencia hit his 15th homer in the seventh.

Valencia was traded by Oakland to the Mariners after last season for right-hander Paul Blackburn. Alonso had 22 home runs for the A's this season before being traded to Seattle on Aug. 6 for outfielder Boog Powell.

"Any time I get to play against an ex-team, you definitely get up for them," Alonso said. "Just compete. You compete and hopefully things go well for you.

"I've played here plenty of games. I feel comfortable. I like it, and I enjoy myself when I'm here."

Khris Davis hit his career-high-tying 42nd home run for the A's (72-85), a two-run shot in the sixth. Marcus Semien hit a solo home run in the first, his ninth blast of the season.

Left-hander James Paxton gave up three runs on six hits, including two home runs, over 5 1/3 innings in a no-decision for the Mariners (77-81), who were eliminated from playoff contention Sunday. He struck out five and walked none in his third start after spending over a month on the disabled list with a strained left pectoral.

Mariners manager Scott Servais said he hadn't yet decided whether Paxton would make one final start on Sunday against the Los Angeles Angels.

"I'm ready to," Paxton said. "Whatever they want me to do. I'm ready to pitch another game. My arm feels good, body feels good."

Emilio Pagan (2-3), Nick Vincent and Edwin Diaz combined to throw 3 2/3 scoreless innings in relief for Seattle. Diaz pitched a perfect ninth for his 33rd save.

A's right-hander Daniel Mengden (2-2) allowed four runs on five hits in six-plus innings. He struck out three and walked three. He entered the game off back-to-back victories, including a shutout of the Philadelphia Phillies on Sept. 15.

Mengden extended his scoreless streak to 19 innings, but Alonso snapped it with his homer in the fourth.

"Not bad," Mengden said of his start. "I left one pitch up to Yonder there. I can't make that mistake. I had the lead, two outs and an 0-2 count. I've got to make a better pitch there."

Davis put the A's ahead 3-2 in the sixth inning with his two-run blast off Paxton. Jed Lowrie singled to right with one out, and Davis crushed Paxton's 95 mph, 1-2 fastball over the right-center-field fence, leaving him one homer shy of setting a career high.

"It would be nice, but at the same time, it's not that much a big deal for me," said Davis, who has 84 home runs in less than two full seasons with the A's.

The Mariners answered with four runs in the seventh to take a 6-3 lead. Alonso lined a leadoff single, and Mengden walked Mike Zunino, ending his night and bringing Valencia to the plate.

Reliever Ryan Dull jumped ahead 0-2 in the count, but Valencia crushed his 91 mph fastball over the left-center-field fence.

"He's a two-pitch guy," Valencia said of Dull. "He's had a lot of success. I've played behind him and he's always done well. I've seen him a lot. I know he's going to stay on the outside part of the plate. I was really looking for a breaking ball, and he tried to throw a fastball by me, and luckily I got it pretty good."

Gordon Beckham singled and scored from second with one out on Ben Gamel's bloop single.

The A's grabbed a 1-0 lead when Semien led off the bottom of the first inning with a home run over the left-center-field wall, his second blast in two nights against Seattle. It was the first career leadoff home run for Semien, and it came on a 1-1 curve from Paxton.

Seattle moved ahead 2-1 in the top of the fourth on Alonso's two-run shot. Nelson Cruz grounded a one-out single to left, and Alonso launched Mengden's 0-2 fastball over the right field fence.

Alonso homered in back-to-back games against the A's.

NOTES: Mariners RHP Felix Hernandez, who has battled right shoulder soreness for much of the season, will not make his final scheduled start Saturday against the Los Angeles Angels, and RHP Mike Leake, who has a sore lat, won't start Friday in the series opener. ... Seattle SS Jean Segura (sprained right middle finger) missed his third straight game and will miss the series finale Wednesday. ... A's RHP Jharel Cotton, who has been nagged by a sore right elbow, will not make his final scheduled start of the season Friday at Texas. ... Oakland 1B Matt Olson (Grade 2 left hamstring strain) was shut down Tuesday for the rest of the season, but manager Bob Melvin said he had already done enough to become the Athletics' everyday first baseman going into next season. Olson hit 24 home runs in 59 games this year. ... A's CF Boog Powell (bruised left kneecap) was shut down Tuesday for the rest of the season.