Bagent has opened the Bears' last three contests in place of Fields, who has been sidelined since dislocating his right thumb Oct. 15 in a loss to the Vikings.
Bears coach Matt Eberflus revealed that Fields is improving.
"He's throwing it better, and he's starting to do more and more and more," Eberflus said. "It's just all improving. The grip strength, the accuracy, the ability to function as a quarterback, it's all right there. It's getting close."
In other injury news, right guard Nate Davis (ankle), fullback Khari Blasingame (concussion), middle linebacker Tremaine Edmunds (knee) and cornerback Terell Smith (illness) have been ruled out of Thursday night's game.
Running back Khalil Herbert (ankle), receiver Equanimeous St. Brown (hamstring) and cornerback Josh Blackwell (hamstring) all practiced in full and were listed as questionable on the injury report. St Brown and Blackwell were activated on Thursday afternoon..
Safety Jaquan Brisker practiced in full and was not given an injury designation, meaning that he's expected to play Thursday night after missing the previous two games with a concussion he sustained Oct. 22 versus the Raiders.
Cornerback Tyrique Stevenson (ankle) was downgraded to questionable Thursday afternoon. The rookie practiced in full all week.
For the Panthers, outside linebacker Brian Burns (concussion/elbow), receiver Laviska Shenault Jr. (ankle), cornerback C.J. Henderson (concussion) and tight end Stephen Sullivan (shoulder) have been ruled out; receiver D.J. Chark Jr. (elbow) is doubtful; and outside linebacker Marquis Haynes (back) and safeties Xavier Woods (thigh) and Von Bell (quad) are questionable.
Roster Moves: The Bears on Wednesday waived cornerback Greg Stroman Jr. and safety Duron Harmon.