Drew Lock could open his rookie season on the injured reserve for the Denver Broncos, says Vic Fangio.

Lock suffered a severely sprained thumb on his throwing hand early in the third quarter of Monday night's preseason loss to the visiting San Francisco 49ers.

The quarterback will neither play nor practice for the remainder of the preseason.

"Obviously because it's his throwing hand and a thumb, that's a pretty serious injury for a quarterback," Fangio said. "It will be some time before we know exactly where he's at and how much time he would miss."