OAKLAND, Calif. (AP) -- Adam Dunn is in a pennant race at last, and what an impression he made on his new team as the September stretch run began.
Dunn provided instant pop for the struggling Athletics, hitting a towering, two-run homer in his debut at-bat for Oakland to highlight a 6-1 win over the Seattle Mariners on Monday in a matchup of playoff contenders.
''I can speak pretty passionately about it, these chances don't come around very often, especially for some of us,'' said the 34-year-old Dunn, who has never played in the postseason. ''We're going to take full advantage.''
Acquired a day earlier in a trade with the Chicago White Sox, the 6-foot-6, 285-pound Dunn immediately became an imposing presence in the middle of Oakland's order. Dunn is the 12th player in Oakland history to homer in his first at-bat with the team.
A 14th-year major leaguer, Dunn homered during a five-run first inning. His drive was a welcome sight for a team that just got swept in a four-game series by the AL West-leading Los Angeles Angels and was shut out for 29 straight innings.
''That's the most excited, anxious, probably call it a little nervous, than I've been in a long time,'' said Dunn, who was thrown off by the celebratory tunnel formed by teammates in the dugout.
The A's broke loose a day after manager Bob Melvin let them have it in a closed-door team meeting. He called his team's play ''embarrassing and ''pathetic'' after the A's totaled just four runs in the sweep at Anaheim.
''They ran the opening kickoff back for a touchdown and the game was over,'' Mariners manager Lloyd McClendon said. ''It wasn't our day.''
Dunn went 2 for 3 batting cleanup as the designated hitter. He provided a nice lift for an Oakland offense that has struggled since dealing Yoenis Cespedes to Boston for Jon Lester on July 31.
With 461 career home runs, Dunn tied Red Sox star David Ortiz for 35th place on the all-time list.
Dunn quickly staked Jason Hammel (2-5) to a lead. Hammel also started the season in Chicago, and was traded by the Cubs in July.
''It had a little bit of a storybook-type theme,'' Melvin said of Dunn's debut. ''We've really been lacking early energy, runs, he comes up to the plate and you're thinking to yourself, 'Boy, wouldn't it be great? And he delivers. You got goosebumps. It was awesome.''
Hammel allowed three hits and struck out five in eight innings to end a three-start winless stretch. It was just his second win since joining the A's from the Cubs on July 4.
Another recent acquisition, Geovany Soto, added a two-run single with two outs in the first that chased Chris Young (12-7) for the shortest start of his career.
A sellout crowd of 36,067 saw the A's win after a stretch in which they lost five of six.
''That's the best crowd I've ever played with,'' Dunn said. ''I'm serious. It's unbelievable. If it's like that every night here, it's going to be a fun little ride.''
Brad Miller homered leading off the sixth for Seattle, which came into the series opener as the American League's top road team.
Robinson Cano's 21-game hitting streak against the A's ended. It dated to Sept. 22, 2012.
Mariners: OF Michael Saunders, on the disabled list since July 11 with a strained left oblique, reported to Arizona to work on strengthening and get some at-bats in simulated games before the club determines the next step in his rehab.
Athletics: CF Coco Crisp will have more trigger-point injections for neck stiffness after colliding with the outfield wall Friday. He hit batting practice right-handed. C John Jaso (concussion) swung in the indoor cage and hopes to hit outside Tuesday.
Mariners: LHP James Paxton (4-1, 1.83) makes his first career appearance against the A's as he looks to win his second straight start. Paxton is 7-1 with a 1.71 ERA in 11 career starts.
Athletics: RHP Sonny Gray (13-7, 3.03) is 4-0 with a 1.10 ERA in his first five starts against Seattle, his most victories against any team.
Mariners: Placed 1B-DH Jesus Montero on the suspended list. The 24-year-old Montero was recalled from his rehabilitation assignment Friday following a verbal altercation with a Mariners scout at a Class A Northwest League game. ... September call-up RHP Carson Smith made his major league debut in the eighth. He threw two pitches and retired Josh Donaldson on a grounder.
Athletics: Reinstated SS Jed Lowrie from the 15-day disabled list and he singled in his first at-bat since Aug. 13. He suffered a hairline fracture of his right index finger Aug. 4.