When the Los Angeles Chargers step onto Empower Field at Mile High this weekend, they can expect to see an unfamiliar face under center for the Denver Broncos. Rookie quarterback Drew Lock has practiced the starter all week and will return from injured reserve prior to Sunday's game.

Broncos head coach Vic Fangio did not officially declare Lock the starter, saying the signal-caller would either start to land on the team's inactive list Sunday. Still, Lock took first-team reps in each of the past three practices, a strong indication of the team's intent to give him the green light.

Though Lock has yet to appear in a regular-season game, the Chargers feel prepared to defend him.

"We have preseason film on him," Los Angeles head coach Anthony Lynn says. "We watched him in college, liked him in college. We know he's a guy that can move around a little bit and create, and he throws with pretty good accuracy as well."

Lock, the No. 42 overall pick in the 2019 NFL Draft, suffered a thumb sprain on his throwing hand during the Broncos' third preseason game. The team held him on the active roster through final cuts before placing him on injured reserve shortly thereafter. By waiting until after the start of the regular season, Denver preserved Lock's eligibility to come off IR and play in 2019.

Even so, Lock never looked like a guarantee to play this season. "I don't think it's vitally important," Fangio said last week. Though Lock became eligible to return from IR after Week 8, he did not begin practicing with the team until this week. With the rookie on the shelf, the Broncos went with veteran Joe Flacco as the starter for their first eight games and journeyman Brandon Allen over their last three.

The Chargers have faced a first-time starting quarterback already this season. During a Week 6 tilt with the Pittsburgh Steelers, undrafted rookie Devlin Hodges filled in for Mason Rudolph, who suffered a severe blow to the head the previous week and had yet to clear the concussion protocol.

Lock played his college ball at Missouri, starting for more than three full seasons for the Tigers. He compiled over 12,000, 99 touchdowns, and 39 interceptions during his collegiate career and earned First-Team All-SEC honors in 2017 and Second-Team All-SEC honors in 2018.

-- Jason B. Hirschhorn is an award-winning sports journalist and Pro Football Writers of America member. Follow him on Twitter: @by_JBH