Santos was acquired during the offseason to serve as the closer, but managed to pitch in just six games before going down with a right shoulder injury.
The hard-throwing reliever attempted to avoid surgery with a lengthy rehab, but when the discomfort refused to subside, he was eventually forced to go under the knife.
"At the time of the surgery, the prognosis and the timeline was to have him ready at some point in Spring Training," manager John Farrell said. "Whether that's game-ready by mid-schedule, that will all be determined when we start getting into more regular activity off the mound."
Santos is in California going through rehab workouts three times a week. He's still unable to throw and is limited to strengthening and range of motion exercises.
The plan is for Santos to begin a throwing program in early December. That falls in line with the Blue Jays' offseason routine for all of their pitchers, which is one of the main reasons why the club is hopeful he'll be back to normal when camp opens.
Santos allowed five runs in five innings while recording two saves. He was acquired from the White Sox for pitching prospect Nestor Molina.