"A's right-hander Ben Sheets was diagnosed with a torn flexor tendon in his elbow that will require surgery and sideline him the rest of the season, manager Bob Geren said before Wednesday's game against the Texas Rangers.

The veteran pitcher feared such a diagnosis when he was placed on the disabled list Saturday and revealed that his elbow has bothered him all season.

This is a reoccurrence of the injury that sidelined Sheets for all of the 2009 season. He underwent surgery for a torn flexor tendon in February 2009, and the A's signed him to a one-year, $10 million contract this past January in the hopes he was recovered and would return to his All-Star form.

Sheets, 32, went 4-9 with a 4.53 ERA in 20 starts, earning praise for the influence and leadership he showed toward his younger teammates but never becoming that dominant No. 1 starter he was brought in to be.

"He's going to be missed, both on the field and off," Geren said. "He's been a great teammate and a pleasant guy to be around." Sheets wasn't at Rangers Ballpark before the A's took the field for batting practice, and was unavailable for comment. Geren said he expected the pitcher to possibly join the team later in the day."