Mike Klis of 9News reported Siemian dislocated his shoulder.
Nicki Jhabvala of the Denver Post reported Siemian's X-rays were negative, and he will undergo an MRI in Colorado on Friday.
After backing up Brock Osweiler and Peyton Manning in 2015, Siemian won the starting job before the start of last year. In 14 games, he finished with 3,401 yards, 18 touchdowns and 10 interceptions. Football Outsiders ranked him 22nd among 34 qualified quarterbacks in DYAR (defense-adjusted yards above replacement).
With Siemian out of action, the Broncos will once again turn to Osweiler after signing him prior to the start of the regular season.
The fact the Houston Texans traded Osweiler to the Cleveland Browns, who then released him, speaks to how much he struggled in his year away from Denver. He has thrown for 701 yards and three touchdowns this season.
The Broncos are in the midst of a disappointing 4-9 season.