An MRI has revealed that Denver Broncos rookie quarterback Drew Lock, who suffered a right thumb injury in the team's preseason loss to the San Francisco 49ers Monday night, has a "bad sprain" and will miss some time, according to NFL Network's Ian Rapoport.

Lock's injury occurred on a third-quarter play where he was tripped by 49ers safety Marcell Harris and subsequently landed on his thumb. The second-round pick (42nd overall) had been competing with veteran Kevin Hogan this preseason for the Broncos backup quarterback job behind former Raven, Joe Flacco, who the team traded for during the off-season. 

In three games this preseason, Lock had completed 31 of the 51 passes he threw for 254 yards with one touchdown and an interception.