ENGLEWOOD, Colo. -- The Denver Broncos went all-in on Drew Lock as the team's starting quarterback almost from the minute the 2019 season ended. That made the job description of Lock's backup complicated. Players such as Cam Newton and Jameis Winston were available, but the Broncos backup wasn't going to be the biggest name or have longest résumé. He wasn't going to be someone who would threaten Lock's status as the starter.

The Broncos wanted a player with some experience, a player they liked when they saw him play and a player with similar athleticism and movement skills to Lock. They wanted a guy to help Lock some, always be ready to play and to make no ripples if Lock hit some rough spots along the way.

The Broncos chose journeyman Jeff Driskel, who they will now lean on as their starter in the coming weeks as Lock recovers from a rotator cuff injury to his right shoulder. Driskel filled in for more than three quarters of Sunday's loss to Pittsburgh when Lock was injured on a sack by Steelers linebacker Bud Dupree. Driskel ended up playing 64 of the offense's 77 snaps in the game. He completed 18 of 34 passes for 256 yards, two touchdowns and an interception.

"I thought in light of the circumstances, coming in there cold, not getting many reps during the week ... I thought he did a good job," Broncos coach Vic Fangio said.

An already difficult season for a battered roster -- the Broncos have lost pass-rusher Von Miller to an ankle injury and learned Monday that wide receiver Courtland Sutton would miss the rest of the season with torn ACL -- got tougher when Dupree chased down Lock from behind to force a fumble. Lock underwent a magnetic resonance imaging (MRI) exam Monday morning and Fangio confirmed early Monday afternoon Lock would miss several weeks.

"Drew's going to be out anywhere from three to four to five weeks," Fangio said. "It all depends on the healing process ... when it's your throwing shoulder, it's going to take time to heal it, it's got to calm down, get his strength back to where he fully has it, and he can operate at 100%."

An offseason plan built around Lock and his learning curve has been derailed some. And while the Broncos thought enough of Driskel to sign him to a two-year, $5 million deal last March, they didn't expect to need him by Week 3 with the Broncos already staring at an 0-2 record.

"As a backup quarterback, it's my job to be ready at all times," Driskel said following Sunday's game. " ... I've been preparing all week, and my job is to give the team a chance to win, and we didn't do that. We've got to make a couple more plays here and there, and maybe it's a different ball game."

Like many backup quarterbacks in the league, Driskel's athletic history gets somewhat lost in the haze as he moves from team to team -- the Broncos are already his fourth NFL team since the San Francisco 49ers made him a sixth-round pick in the 2016 draft. But Driskel was once the top prep quarterback prospect in the nation when he chose the University of Florida.

But his career for the Gators was a roller-coaster ride -- 11 wins as a sophomore, then losing his job, then going in and out as the starter while dealing with injuries. He finally transferred to Louisiana as a senior, hoping for one last chance to get the attention of the NFL's talent evaluators, and threw for 4,026 yards during that 2015 season.

The Broncos' decision-makers saw him face Denver once in the NFL -- a 2018 Denver win over the Cincinnati Bengals when Driskel threw for 236 yards with a touchdown and an interception. The Broncos had also reviewed his three starts with a struggling Lions team last season when Driskel completed 59% of his passes with four touchdowns and four interceptions.

When Driskel signed with the Broncos in March he was asked to describe his game and offered:

"I don't know if there's a certain way to describe it. I always try to play within the system. You try to do what's practiced. You try to just be efficient and move the chains. Sometimes things don't play out on the field like they're practiced or like they're drawn up. You try to extend plays and that's where you see a lot of big plays ... I'm an athletic guy who's willing to use all the gifts that I have and be effective."

The Broncos get the Tampa Bay Buccaneers on Sunday before a quick turnaround for a Thursday night game against the New York Jets Oct. 1 at MetLife Stadium. They then get a 10-day window before a Week 5 game Oct. 11 in New England, but don't have their bye until Week 8. They agreed to terms Tuesday on a one-year deal with Blake Bortles, but he won't likely be available until at least Week 4. Until Lock returns somewhere in there, Fangio said the Broncos will try to find a way to make it work.

"I don't think it's a wholesale change in the offense, it might look different to others," Fangio said. "But it's stuff we've been practicing and have had in that maybe we'll lean on more with Jeff in there."