Bears offensive coordinator Luke Getsy said he had faith in undrafted rookie quarterback Tyson Bagent as he prepares to make his first NFL start Sunday against the Raiders.

“He has a lot of confidence,” Getsy said Thursday. “He works his butt off, so the preparation is what gives him his confidence. .... He’s put the work in.”

Getsy coached Bagent when he was the head coach of the American team in the Senior Bowl during the offseason. At first, he said, he thought Bagent was a nervous player. By Wednesday or Thursday of game week, though, it was clear he’d been studying the playbook so well that he knew the offense.

Fields dislocated his right thumb in the third quarter Sunday and was replaced by undrafted rookie Tyson Bagent, who will start against the Raiders. The Bears said they want to wait until the end of this week to decide whether Fields will have surgery or go on injured reserve.

“There’s nobody in this building that’s going to work harder at getting himself back ... than Justin,” Getsy said.