"He won't throw for five days, but we'll start him back up after that," Geren said. "It won't set him back too far. I don't know how to classify it, but we're very optimistic about the results."
Because Wuertz is almost guaranteed to start the season on the disabled list, he won't be able to return to the mound until April 10 at the earliest, as the team can backdate the injury to March 26.
Meanwhile, fellow relievers Andrew Bailey and Craig Breslow, whom have both been nursing sore elbows, made one-inning appearances in Monday's game for the first time since March 14.
Bailey, who set an Oakland rookie record with 26 saves en route to being named the American League Rookie of the Year last season, struck out one and gave up one hit -- a go-ahead home run to Seattle's Franklin Gutierrez in the ninth.
"I was trying to establish my fastball and feel back on the mound," Bailey said. "I felt it went outstanding, even though we lost.
2010 Spring Training - null
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Spring Training Info
"I feel back on schedule. Now that that's over with, you can go back to working on your other stuff, focusing on command and your secondary pitches."
The A's right-hander solely threw fastballs at the beginning of his outing, but after watching a few hard-hit balls he deemed "missiles" pass him, he mixed it up with a couple cutters and a curveball in an effort to "not feel hesitant out there."
Breslow, who also witnessed his only surrendered hit turn into a home run, knows the feeling. The A's southpaw said he felt great physically but was holding back a touch mentally.
"Everything felt good," Breslow said. "Now it's just a matter of feeling comfortable out there again. I think that just comes with time, so I'll keep improving my next couple times out."
Bailey and Breslow's pain-free outings, along with a clearer timetable for Wuertz, now give the A's a greater sense of comfort surrounding their bullpen situation.
"From a bullpen standpoint, today was great," Bailey said. "Mike got some good news with his arm, and Breslow and I were back out there, and we both felt good.
"That's my fifth appearance and we can go from there. There's still some time to get used to game action again, but I'll definitely be ready for Opening Day."