Blount injured his knee during an October 9 game against San Francisco and sat out last Sunday's contest against New Orleans. He did not practice this week and the team has a bye next Sunday, which would give him an extra week of rest.
Earnest Graham will make the start against the Bears. He ran for 109 yards in last week's 26-20 win over New Orleans.
In five games this season, Blount has rushed for 328 yards and three touchdowns.
McCoy is bothered by an ankle injury and missed Friday's practice after being a limited participant on Wednesday and Thursday.
The Bucs will also be without center Jeff Faine and wide receiver Sammie Stroughter against Chicago. Faine suffered a biceps injury last week and Stroughter continues to be sidelined with an ankle issue.