ENGLEWOOD | The Denver Broncos are bringing rookie quarterback Drew Lock back to practice Tuesday to see if he’s going to be able to play this season.

The second-round draft pick from Missouri went on IR to start the season after spraining his right thumb in an Aug. 19 preseason game against San Francisco.

His return will start a 21-day clock in which the Broncos (3-6) must decide whether to put him on the active roster or send him back to IR, ending his season and delaying his evaluation until 2020.

It’s that three-week window that prevented coach Vic Fangio from bringing Lock off IR two weeks ago when Joe Flacco (neck) went on IR and 27-year-old waiver wire claim Brandon Allen led Denver past Cleveland 24-19 in his first NFL start.

Fangio didn’t want the 21-day clock ticking on Lock during the Broncos’ Week 10 bye, so he waited until this week to bring him back.