Knox, who is recovering from spinal fusion surgery, is scheduled to start the regular season on the physically-unable-to-perform list, meaning he couldn't return in the first six weeks, and there's a good chance he won't play in 2012, the Tribune said.
Knox has had to wear a back brace since the surgery and walks with a limp.
A source told the Tribune there had been more structural damage than what had been anticipated initially.
Knox couldn't be reached for comment.
He was injured in December while trying to recover the ball after fumbling it in a game against Seattle.
Last season, Knox caught 37 passes for 727 yards, averaging 19.6 yards per catch, and two touchdowns. He returned 15 kickoffs for 397 yards for an average of 26.5 yards per return.