But Allen's 21-yard touchdown pass to a leaping Courtland Sutton with 6 minutes, 9 seconds left in the first quarter was the launching point for a winning debut for Allen as the Broncos used Allen's play and a stingy red zone defense to key a 24-19 win over the Cleveland Browns at Empower Field at Mile High.
"I made some dicey throws Courtland bailed me out a couple times on,'' Allen said. "... When Courtland caught that pass, I felt pretty good because I made a pretty terrible pass, and he helped me out and caught that touchdown.''
It was a day for which Allen waited 42 months, from the time the Jacksonville Jaguars made him a sixth-round pick in the 2016 draft to Sunday, when he took his first snap in a regular-season game. He finished 12-of-20 passing for 193 yards and two touchdowns in relief of Joe Flacco.
The win nudged the Broncos to 3-6 as they head into their Week 10 bye. Denver equaled its best scoring output of the season; the Broncos scored 24 points in a Week 4 loss to the Jacksonville Jaguars.
"[The] guy's got moxie, guy's got moxie,'' Broncos defensive end Derek Wolfe said. " ... Just the way he carries himself. Adversity either makes you tougher, or it makes you quit. And look what it did for him. It made him tougher. It made him a better football player. Who knows what it means for him.''
Allen was forced into duty when the 34-year-old Flacco suffered a herniated disc in his neck, an injury Flacco said he believed he aggravated in the team's loss to the Indianapolis Colts last week. Flacco was placed on injured reserve this past week, and Allen, who was claimed on waivers from the Los Angeles Rams just before the start of the regular season, was pushed into the starting lineup.
The Rams play a similar scheme on offense, which was one of the reasons the Broncos claimed Allen in the first week. That comfort level showed, at least after some initial jitters in a wobbly-looking three-and-out to open the game, as Allen eventually led the Broncos on three touchdown drives.
"Nervous energy would be the best way for me to describe it,'' Allen said. " ... Once you get playing, get in there and get hit one time, you get in there and get going.''
"I thought he ran the offense good,'' Broncos coach Vic Fangio said. "Showed a little mobility, made some good throws, missed a few too. We're not ready to put him in Canton yet, but overall pleased with the way he played.''
The Broncos kept much the same playcalling for Allen as they had shown with Flacco in the season's first eight weeks, with plenty of three-wide-receiver sets mixed in with the two-tight-end and two-back sets. The Broncos put Allen in the pistol from time to time instead of the shotgun and, despite Allen's inexperience, wanted to play aggressively.
Allen's 21-yard toss to Sutton, a ball Sutton snatched over top of the Browns defender, finished the Broncos' second possession of the game. Then on the Broncos' fourth possession, Allen threw a quick slant to rookie tight end Noah Fant, and Fant broke three tackles to finish a 75-yard catch-and-run touchdown.
Fant had his first career 100-yard day -- 115 yards on three receptions -- and running back Phillip Lindsay had 92 yards rushing, including a 30-yard touchdown run and a 16-yard run out of the Wildcat formation just before the two-minute warning to seal the win.
"Obviously, 24 points is not an area we've [gotten] to too many times, so that's good,'' Fangio said. "Thought we called a good game, made some adjustments in the way we called a game, and it paid off.''
The Broncos added a 95-yard scoring drive in the third quarter -- their third touchdown drive of the game -- and that meant Allen was the first quarterback to lead his team on a touchdown drive of 95 or more yards in his first career game since Marc Bulger in 2002.
Allen also became the second Broncos quarterback in franchise history to start his first career game and see the Broncos win. John Elway made his NFL debut against the Pittsburgh Steelers in 1983, a game the Broncos won 14-10, but Elway was pulled from that game after he was 1-of-8 for 14 yards and an interception.
Fangio presented Allen with the game ball Sunday in the locker room.
"It was special,'' Allen said. "... But the game ball should have gone to the entire team.''
All of the quarterback questions will come later. Allen will start the Broncos' Week 11 game in Minnesota and the Week 12 game in Buffalo. Broncos coach Vic Fangio has said that rookie quarterback Drew Lock, who is on injured reserve recovering from a right thumb injury suffered in preseason, is expected to return to practice in Week 11 after the team returns from the bye.
Lock can practice for up to three weeks before the Broncos must decide to keep him on injured reserve or put him on the roster. Lock was a second-round pick -- the 42nd overall -- in this past April's draft.
"It's tough. There's a lot of guys that would tell you this league is tough,'' Allen said. "You get cut, traded, waived, whatever. It's all about perseverance, getting that opportunity to see what you can do. A lot of guys don't even get that opportunity ... My whole thing ... I take everything one day at a time, whatever happens, happens ... Whether it's one more game or 10 more games, I'm going to take advantage.''