OAKLAND, CALIF. - The good news is that Twins righthander Liam Hendriks identified a mechanical flaw during his outing on Wednesday and made the adjustment.

The not-so-good news? It was when he made the adjustment.

"It was during Chris Carter's at-bat in the fifth," Hendriks said.

Carter was Hendriks' final batter of the day.

Hendriks exaggerated the point that he found a little bit of a groove near the end of his outing on Wednesday, but he still wasn't up to par as Oakland whipped the Twins 5-1 to take two of three games in the series and send the Twins to a season-worst 21 games under .500.

Hendriks, making his first start for the Twins since July 2, gave up four runs over five innings on six hits and three walks with two strikeouts.

"He competed," Twins manager Ron Gardenhire said. "He didn't let the innings get too out of hand. He gave up a few runs here and there. But you have to be a little bit better than that with the strike zone and work ahead of more hitters.

"But like I said, he competed. He got out of some jams he created for himself, so there's a step in the right direction."

Oakland got an RBI single from Josh Reddick in the first to open the scoring. The Twins scored their only run of the game in the second, on Drew Butera's grounder. Yeonis Cespedes hit a two-run single in third, and the A's never looked back as they moved to a season-high 11 games over .500.

The Twins, meanwhile, have to finish 12-27 to avoid 100 losses. Yes, it's that time of year.

Hendriks can do his part to help the Twins avoid the century mark -- and improve his candidacy for next year's rotation -- if he can finish strong.

"This was a little bit better," Hendriks said. "I was attacking guys and wasn't given a lead and then blowing it. It was just one of those days where I needed to keep us in the game, and it was unfortunate I could only last five. I was at least happy to get through the fifth, which I didn't last time."

Lefthander Tommy Milone held the Twins to two hits over eight innings to improve to 10-9 for the season.

Surgery for BensonThis has turned out to be a lost season for outfielder Joe Benson, considered to be one of the Twins' top prospects heading into the season.

Benson on Monday will have surgery on his left knee to remove loose bodies. It's the same knee on which he had surgery last year to repair a slight meniscus tear.

Benson, 24, already has had surgery this season to remove the hamate bone from his wrist. That came after he got off to an awful start at Class AAA Rochester and was demoted to Class AA New Britain.

In stops at four minor league outposts -- he also played for the GCL Twins and the Class A Fort Myers Miracle during rehab stints -- Benson batted .206 in 76 games with six homers and 36 RBI. This after being promoted from New Britain to the majors late last season.

"Unfortunately, he's been hurt the last couple of years," said Jim Rantz, Twins director of minor leagues. "He's got to stay healthy."

Evaluation tourTwins General Manager Terry Ryan has moved from Class AAA Rochester to Class AA New Britain as he evaluates players who might deserve a September callup.

The fact that Ryan is with New Britain suggests that outfielders Oswaldo Arcia and Aaron Hicks might be among those under consideration. Arcia played half a season at Fort Myers before moving to New Britain, batting .325 with 14 homers and 84 RBI overall. Hicks, the Twins' first-round pick in 2008, is batting .283 with 12 homers and 55 RBI with 29 steals at New Britain.

The Twins also are firming up commitments for winter ball and are waiting to see which players will take part in the Arizona Fall League. Hicks is a candidate to play winter ball this offseason. Benson, following surgery, and righthander Kyle Gibson could wind up in the AFL. AFL rosters will be announced next week.