OAKLAND -- As Brandon Moss watched the ball he'd just pummeled sail long and far over the Oakland Coliseum's right-field wall Saturday afternoon, he soaked in the nirvana of the A's latest, greatest moment of a storybook season.

"There isn't a much better feeling than that," said Moss after his 10th-inning, three-run home run gave the A's a wholly fantastical 7-4 victory over the Seattle Mariners. "When you're playing the game as a little kid in your backyard, that's kind of what you dream of doing."

It's the same little-kid dream that Josh Donaldson made come true just an inning earlier, when he tied the game with a crushed home run to center field, a one-out blow he admitted he was trying to hit when he strode to the plate with a man on and Oakland trailing 4-2.

There is still work to do for these A's, but this latest boom-boom-out-go-the-lights victory had the feeling of "The One" that will get them over the bar to the postseason. It was Win No. 90 -- count 'em, 90 wins for this band of rookies and rejects -- but in terms of drama and importance, it just might have been No. 1 on the 2012 charts.

The home runs by Donaldson and Moss stole the show, but so much more went into Oakland's major league-best 14th walk-off win. Coco Crisp's four hits. Five relievers throwing 62/3 innings of shutout ball. Yoenis Cespedes displaying more uncanny athleticism, scoring from first base on a single. Adam Rosales and Moss making lay-out airborne snares of line drives in the late innings.

In short, there were a lot of nice stamps on the 90th, a number that did not go unheeded by manager Bob Melvin.

"Boy, that's pretty terrific, it really is," Melvin said. "It's a nice round number. We want more, but it's a nice little feather. We don't plan on stopping there, but that's a nice number."

"It's a great accomplishment," added A's closer Grant Balfour (3-2), who pitched a scoreless 10th and earned the victory. "Ninety wins is great ... and 94 will be even better."

Early on, it looked for all the world that the 90th would have to wait another day. Seattle starter Jason Vargas, a thorn to the A's in six starts against them this season, pitched seven innings of five-hit ball with no walks and seven strikeouts. He would had allowed no runs had it not been for Cespedes' derring-do sprint from first to home on Moss' fourth-inning single.

But Seattle had jumped to a 4-0 lead against starter Dan Straily, thanks to throwing errors by Moss and Cespedes in the second and homers by Kyle Seager and Michael Saunders in the top of the fourth.

Oakland got a run closer in the eighth on a Moss RBI double, but the inning ended on a downer when Stephen Drew got thrown out at home on the hit. That took it to the ninth against Seattle closer Tom Wilhelmsen, who got the Mariners out of the eighth and was looking for his 30th save of the season.

Wilhelmsen struck out pinch-hitter Seth Smith to start the ninth, but then walked Reddick in advance of Donaldson. So what was Donaldson thinking as he stepped into the box?

"I mean, I was really trying to hit a home run," he said. "I don't know what else to say. The first pitch, he throws me a heater. I felt I took a pretty good swing. The next pitch, I didn't think he'd come back with a heater, so I was sitting offspeed. I knew he had a big breaking ball and I saw it pop up and I put a good swing on it."

It was Donaldson's ninth homer of the season, but none have bigger. Similarly, Moss' 21st in the 10th -- Oakland's sixth walk-off via the home run -- put them in a position where they could conceivably clinch an American League wild-card spot Sunday.

All Moss really needed was a single after Crisp had opened the inning with a single against lefty Oliver Perez (1-3), and Cespedes drew a four-pitch walk against Seattle's fifth pitcher, hard-throwing righty Stephen Pryor. Up stepped Moss, with a clear idea in his head about what he wanted to do.

"If I'm looking for anything but a fastball from a guy who throws that hard, I'm probably in trouble," Moss said. "(Friday) night he got me to pop up with the bases loaded on a pitch that was just a little high, so I was just really trying to get a pitch down and in, something I could get the barrel to, and it just happened to be the first pitch. I ended up hitting it better than I thought I would have hit it."

  • Pitcher Brett Anderson (oblique strain) threw off flat ground from a distance of 120 feet and could have a bullpen session off the mound as early as Monday. Anderson won't be available for the rest of the regular season but could be back for a prospective division playoff series depending on how quickly he progresses.

    "We just have to continue monitoring him," Melvin said. "We're trying to keep our options open, but we don't want to rush him."

    A.L. West race

    W L Pct. GB
    Texas 92 65 .586 --
    A's 90 68 .570 2 1/2

    A.L. Wild-card race

    W L Pct. GB
    Bal/NY 91 67 .576 --
    A's 90 68 .570 --
    L.A. Angels 87 70 .554 2 1/2
    Tampa Bay 87 71 .551 3
    Note: New York and Baltimore are tied atop A.L. East; top two non-division winning teams earn wild-card berths.

    Magic number

    3 Combination of A's victories and Angels losses needed to clinch a wild-card spot.