Hillis had a drama- and injury-filled second season in Cleveland after rushing for 1,177 yards in 2010.
He won a nationwide fan vote to be the cover figure for "Madden NFL 12," but then rushed for just 587 yards last season.
Hillis sat out last Sept. 25 against Miami with a bout of strep throat, an incident that didn't sit well with some teammates. He also missed a treatment for his ailing hamstring when he left during a work week to get married.
Hillis, a seventh-round pick out of Arkansas in 2008, also played two seasons with Denver.