Thomas, the first receiver selected in last year's draft, is expected to be out six to eight months.
Neither Thomas nor his agent, Todd France, responded to messages from The Associated Press.
When Fox was hired last month to oversee the Broncos' massive makeover, he mentioned the deep receiving group as the primary luxury he was inheriting in Denver.
Fixing the defense remains priority No. 1 in Denver, but the Broncos will have to at least consider taking a wide receiver in the draft, where they have just a half-dozen picks, three of which are in the top 50, including the No. 2 overall selection.
Thomas was selected 22nd overall out of Georgia Tech a year ago, three spots ahead of Denver's other first-round pick, quarterback Tim Tebow.
Thomas has been dealing with one injury after another since deciding to go pro after three solid seasons at Georgia Tech.
He fractured his left foot in pre-draft workouts and just when he began to show flashes of being able to use his 6-foot-3, 230-pound body and athleticism to present matchup problems and have a big impact, he tore scar tissue in the foot during a training camp scrimmage and was never really the same.
He missed the rest of camp and the opener and although he caught eight passes for 97 yards and a touchdown in his debut against Seattle a week later, he never tallied more than three catches in any other game.
He was knocked out of one game with a concussion while returning a kickoff and was also sidelined for the final five weeks of the season with a sprained ankle.
Thomas played in 10 games, starting twice and finishing with 22 receptions for 283 yards and two scores. He also returned 16 kicks for a 24.9-yard average.
CBS4 in Denver first reported Thomas' injury on Twitter.
Copyright 2011 by The Associated Press