Eric Chavez will begin rehabilitating his back in approximately three weeks, A's assistant general manager David Forst said Wednesday, one day after Chavez underwent surgery in Los Angeles to repair a bulging disk. Forst said Chavez should be able to continue his rehab from last month's shoulder surgery sooner than that. The team is not providing any timetable for Chavez's return to baseball activity, but it is generally thought that he will be ready to play when the regular season begins. Dr. Robert Watkins performed the back surgery and said it went very well, Forst said.