PHOENIX -- Arizona third baseman Chad Tracy will undergo season-ending surgery on his right knee on Thursday.

The announcement came a week after All-Star second baseman Orlando Hudson underwent surgery on his thumb, ending his season.

Tracy had struggled with the injury for much of the season, going on the disabled list Aug. 15. He pinch hit on Sunday but couldn't do knee bends when he arrived at the ballpark the next day.

Manager Bob Melvin said an MRI exam on Monday revealed fragments in the knee. But Tracy said he wasn't sure what was wrong and that doctors might not know the extent of the damage until they operate.

"I could wake up with a short recovery or I could wake up with a long recovery," he said.

Tracy is hitting .264 with seven homers and 35 RBIs in 76 games. He's been replaced at third base by Mark Reynolds, promoted from Double-A Mobile in May.