Walton's season ended on Oct. 1 last season when the Broncos placed him on injured reserve with a broken and dislocated left ankle.
Three sources told the Post that Walton's most recent surgery was to replace hardware inserted into his ankle during a surgery to repair last year's injury.
The newspaper reported that the Broncos are optimistic that Walton will be able to return by late October or early in November. However, if he suffers any complications in his rehab from the surgery, he might miss the entire 2013 season.
Walton had missed most of the Broncos' workouts this offseason and had just returned to participate in drills on a limited basis during last week's minicamp.
Before his injury, the 26-year-old Walton had started all 36 games of his career since being selected by the Broncos in the third round of the 2010 draft.