PHOENIX -- A's All-Star right-hander Justin Duchscherer has been told to not pick up a baseball for at least a week, increasing the likelihood that he'll open the season on the disabled list.

Oakland's No. 1 starter, Duchscherer has been experiencing discomfort in his right elbow for the past two weeks. He hasn't thrown off a mound since Thursday, and on Tuesday he was examined by Dr. Doug Freedberg, who ordered a contrast MRI.

Duchscherer on Wednesday morning said the MRI didn't show "anything major," adding that the only irregularity identified was something he's known about since he was a teenager.

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"When I was 13, I did something to a ligament in there and I think it pulled a little piece of bone off," Duchscherer explained. "It's all healed up, and it's never bothered me, but it just looks different than normal on the MRI."

A's manager Bob Geren confirmed that there were "no significant findings" in the MRI, but the team is seeking a second opinion. Geren and Duchscherer said the MRI results will be sent to Dr. Lewis Yocum, a noted elbow specialist.

"We're in the process of setting that up," said Geren.

Despite a slew of ominous signs, Geren had maintained an optimistic outlook on Duchscherer's status through Tuesday, taking solace in the fact that his ace hadn't been shut down.

Now that Duchscherer has been shut down, Geren has changed his tune.

"His Opening Day start is definitely in jeopardy," said the skipper.

What won't change is the way the A's evaluate their candidates for the No. 5 spot in the rotation. But Geren did concede that the candidates are essentially auditioning for the No. 4 spot, as well.

Among the top candidates are non-roster righties Edgar Gonzalez and Jerome Williams, and lefty prospects Gio Gonzalez and Josh Outman.

Duchscherer, a converted reliever who missed 42 games with elbow tendinitis in 2006 and has dealt with similar issues at various times during the past three seasons, said the pain he's experiencing now is not unlike the pain that shelved him in 2006.

"It's the same kind of pain, but it's more pain," Duchscherer added. "It doesn't bother me at all except when I'm throwing, and even then it doesn't bother me until I start throwing at about 80-percent intensity. But once I get up to 80 percent, it's pretty bad -- to the point that I can't even bend my elbow."

Duchscherer, 31, has been on the disabled list four times in the past three seasons, and he's also missed significant time with various injuries that didn't require a trip to the DL.

To say that Duchscherer's frustrated right now would be a massive understatement.

"The only thing I can do is come to the field every day and just run," he said. "The worst part is not knowing exactly what it is. I'd have liked to have heard something definitive [Tuesday], one way or another, but it's still an unknown.

"I'm trying to stay positive, but it's hard to do that when we still don't know exactly what's wrong. ... It's brutal."