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CHICAGO -- With starting quarterback Aaron Rodgers battling calf and hamstring injuries, the Green Bay Packers are promoting rookie quarterback Joe Callahan to the 53-man roster ahead of Sunday's game against the Chicago Bears at Soldier Field, a source said.

Rodgers, who injured his right calf last Sunday against Seattle and his left hamstring Nov. 28 at Philadelphia, didn't practice Wednesday or Thursday and was listed as questionable Friday on the injury report.

All indications this week from Rodgers and coach Mike McCarthy were that Rodgers would play against the Bears on Sunday, when game-time temperatures are expected to be around zero degrees. Rodgers still is expected to start.

If Rodgers were unable to play or had to leave the game, second-string quarterback Brett Hundley -- who took most of the first-string snaps this week in practice -- would get the nod. Adding Callahan from the practice squad likely is a precautionary move in case Hundley also were to be injured.

The Packers confirmed Callahan's promotion later Saturday and announced that linebacker Carl Bradford had been released.

Callahan, an undrafted free agent from tiny Wesley College in Delaware, impressed the Packers during training camp and made the initial 53-man roster. After being released early in the season, he was claimed by the New Orleans Saints and also spent time with the Cleveland Browns before being re-signed to the Packers' practice squad.

During the 2013 season, the Packers lost Rodgers to a broken collarbone in a game against the Bears and then also lost backup Seneca Wallace to injury, leaving them with third-stringer Scott Tolzien.