Mitchell, who spent most of the season at Triple-A Albuquerque, has played through the injury since May with the assistance of injections and was already scheduled for the debridement procedure once the season ended. But it became inflamed over the weekend and the decision was made not to wait.
The surgery will be performed by Phoenix hand specialist Dr. Don Sheridan and will require six to eight weeks for recovery, which should allow Mitchell to play at least part of the winter ball season in Venezuela, as he planned. He was expected to work on catching there to increase his value.
Mitchell joins Jonathan Broxton (elbow surgery), Casey Blake (neck surgery), Rubby De La Rosa (elbow surgery), Jon Garland (shoulder surgery), Andre Ethier (knee surgery), Vicente Padilla (neck surgery) and Juan Uribe (sports hernia surgery) with season-ending injuries.
In other medical news, Tony Gwynn, out since Sept. 15 with a bruised left shoulder, was available Monday night for pinch-hitting and defense, according to manager Don Mattingly.