ARLINGTON -- Andrew Bailey's return to the mound appeared to be coming sooner rather than later, but the A's closer delivered a dose of unexpected news Thursday night by revealing that he has a right intercostal (rib) muscle strain.

The right-handed reliever, healthy all season up to this point, has been sidelined since July 20 when he experienced back spasms during two innings of work against Boston. Somewhere between then and now, though, the back pains turned into rib pains.

"Once the back spasms kind of relaxed and got pushed aside," Bailey said, "my ribs started hurting."

Such is life in the A's clubhouse, where the disabled list has already been used 19 times. Bailey could very well be the 20th as soon as Friday, when Oakland will be looking to free up a roster spot for Brett Anderson, who is scheduled to be activated and start against Chicago.

Kurt Suzuki missed two weeks with the same intercostal injury earlier in the season, as did Coco Crisp, who stayed on the DL for almost a month.

"It's the year of the intercostal injury," Bailey said. "There always seems to be a common injury every year, and I guess I got bit by it. It's unfortunate."

Bailey was diagnosed by Dr. Keith Meister, the Rangers' team physician, during Oakland's 7-4 loss to Texas on Thursday. Just 24 hours earlier, Meister told right-hander Ben Sheets he has a season-ending torn flexor tendon in his elbow.

Thus, news didn't come in the best form for the A's on their three-game road set in Texas -- which also resulted in a series loss -- but Bailey is hoping his setback isn't very serious.

"[Meister] said it's one of those things where I could wake up and feel great," Bailey said, "or it can be a yo-yo thing if I push it."

Bailey, who joined Trevor Cahill at the All-Star Game earlier this month, has not allowed a run in 13 of his past 15 appearances, a time span in which he's compiled a 1.10 ERA. He has a 1.56 mark on the season, good for fifth among all American League relievers.

Worth noting

The official announcement of first-round Draft pick Michael Choice's $2 million signing with the A's, as confirmed Wednesday pending a physical by Choice's agent, was expected Thursday. However, an A's representative said it likely won't come until Friday at the earliest. ... Landon Powell received his first start at catcher since July 18, while Kurt Suzuki was placed in the designated hitter's spot Thursday against the Rangers. Daric Barton received a day off, with Adam Rosales getting the start at first base to provide the A's a heavy right-handed-hitting lineup against Texas lefty C.J. Wilson. ... Geren said Conor Jackson (right hamstring) is progressing well in Arizona and had "the best day he's felt" Wednesday. However, there is still no timetable for his Minor League rehab assignment. ... Rajai Davis, who stole his 32nd base of the season against the Rangers on Thursday, is just the fifth player in Oakland history with at least two 30-steal seasons. He has also hit safely in 18 of his past 19 games against the Rangers.