PHOENIX -- Rich Harden could only chuckle and shake his head good naturedly at his latest predicament.

Yes, Harden is hurt again.

The Oakland Athletics right-hander is expected to miss two weeks of spring training after experiencing stiffness in the lat muscle below his pitching arm when he tried to throw Tuesday. Two days later, manager Bob Geren said Harden wouldn't pitch again until he is pain-free -- and the training staff figures that will take at least a couple weeks.

"We evaluated him the last two days," Geren said before Thursday's workout. "I just look at it as a setback. I don't look at it as terrible news. ... We'll see when he gets pain-free. It definitely could affect that fifth starter spot. Hopefully it's just a minor setback."

The news that he would be shut down is a tough break for Harden, who is back for a second stint with the A's hoping to crack the rotation in what stands to be quite the competition for the No. 5 job. He was forced to stop his bullpen session after 10 to 15 pitches.

"It's frustrating, but I still feel I can go out there and be healthy for a full season after that," said Harden, who has dealt with this same injury before. "It is what it is. I know I can come back and still pitch well."

Geren acknowledged the 29-year-old Harden, who had thrown three other times off the mound before Tuesday, may have a tougher time cracking the rotation now.

"Really, that's out of my control now," Harden said. "I've got to focus on getting back and getting healthy, building up. The hard part is not pushing too hard too early. ... I was excited to get going because I feel so good."

Harden received a $1.5 million, one-year contract in December to rejoin the A's. He went 5-5 with a 5.58 ERA in 20 appearances and 18 starts for the Texas Rangers last season, when he struggled with injuries and control. After beginning the season as the Rangers' No. 2 starter, he walked 62 batters in 92 innings.

Harden worked this winter in Arizona with A's pitching coach Ron Romanick, regularly watching video from his standout 2008 season. That year, Harden went a combined 10-2 with a 2.07 ERA in 25 starts between Oakland and the Chicago Cubs. Chicago acquired him on July 8, 2008, in a trade with the A's.

Training with Romanick, Harden said he has improved his mechanics in a way he hopes will help him stay healthy in the long run.

"Maybe my body wasn't used to throwing correctly mechanically," Harden said. "I was sound and throwing solid. I had more extension with a better arm slot and better arm angle. Maybe I had a slight weakness in that area."

Harden spent two stints on the disabled list in 2010, first from June 12 to July 30 with a strained left gluteal muscle and later with right shoulder tendinitis.

Harden went 1-2 with a 2.45 ERA in only 25 2/3 innings in 2007 because of an inflamed right shoulder and didn't pitch after July 7 that year. He threw two simulated games late in the season with the hopes of making two final starts but ultimately decided it wasn't worth risking further injury.

He was 4-0 in nine games in 2006, spending time on the disabled list with a strained back and then a strained elbow ligament.

Harden is thrilled to be back with a club that knows him so well -- and knows his injury history.

"It's the right place," he said.