OAKLAND, Calif. — The Minnesota Twins have begun what could be a difficult ending to a difficult season.

Oswaldo Arcia homered and drove in six RBIs as the Twins lost 11-7 Sunday to the Oakland Athletics, who celebrated a second straight AL West title.

Minnesota could watch two more teams clinch postseason berths against them. The Twins open a three-game series against AL Central-leading Detroit before four final games against Cleveland, which is hoping to secure a wild-card spot.

“They’re locked in right now. We aren’t,” said Twins starter Cole De Vries, who allowed six runs in two innings.

Coco Crisp hit a three-run homer, Daric Barton and Jed Lowrie each had a solo shot and Oakland turned the Twins into a footnote during another scintillating September run.

The A’s clinched their 16th division crown and 25th postseason appearance when Texas lost 4-0 at Kansas City during the game.

Sonny Gray (4-3) gave up four runs and seven hits in five innings for Oakland, calling it “one of the most nerve-racking starts I’ve ever had.” The A’s scored six runs in the second inning and one in each of the next five.

“The ball was flying out of here,” Twins manager Ron Gardenhire said. “We didn’t make many pitches.”

The obstacles Oakland has overcome could serve as an example for Minnesota moving forward.

The A’s had the fourth-lowest opening day payroll at about $65 million. They have a roster full of mostly anonymous and up-and-coming players. And their home is an old, dual-sport stadium where sewage has leaked in the clubhouses and the dugouts in one sickening scene after another.

The A’s still emerged as the team to watch this October in the Bay Area with the San Francisco Giants — winners of two of the last three World Series titles — out of the postseason picture. Oakland has won four straight and 13 of 16 to move a season-high 30 games over .500.

“I don’t know how anybody could be surprised this year,” outfielder Brandon Moss said.

After tearing down the plastic sheets and putting away the bubbly in the clubhouse when the Rangers won Saturday night, the A’s left nothing to chance.

In the second, De Vries (0-1) walked three straight batters with two outs before Oakland’s outburst. Eric Sogard blooped a two-run single, Crisp hit his 22nd home run and Josh Donaldson doubled to put the Athletics ahead 6-1 and whip the green-and-gold clad crowd into a frenzy.

With the Twins batting in the third, word started to circulate around the Coliseum of Justin Maxwell’s two-out grand slam that beat the Rangers in the 10th inning to seal the division title for the A’s. Some players, noticing the high-fives and hollers in the stands, kept glancing at the manual scoreboard in left field.

The excitement subsided briefly when Arcia hit a three-run homer in the third to slice Oakland’s lead to 6-4. He also had an RBI single in the first and a two-run single in the ninth to tie Tony Oliva for the most RBIs in a game by a Twins rookie.

“I felt good. I was thinking about my approach and using the middle of the field,” Arcia said through an interpreter. “That helped me see the ball better. Every at-bat is a learning experience. I’m trying to get better.”

So is Minnesota. After Arcia’s homer, Maxwell’s slam was shown on the video board between innings, setting off chants of “Let’s go, Oakland!” from the announced crowd of 30,589.

A’s players shared subtle hugs in the dugout, and the Twins could only watch.

NOTES: Twins general manager Terry Ryan said C Joe Mauer (concussion) had another good day of workouts. The club hopes Mauer can begin baseball activities soon. … Only the Yankees (51) and Dodgers (27) have more postseason appearances than the A’s. … RHP Mike Pelfrey (5-13, 5.34) starts for the Twins in their series opener with the Detroit Tigers on Monday night. Justin Verlander (13-12, 3.66 ERA) starts for the Tigers.