CHICAGO — Prior to Thursday, Denver Broncos quarterback Trevor Siemian had never played a football game inside the Windy City limits.

But the Connecticut-born, Orlando-bred Siemian knows it well, having made the trek to play his college games up the road a few miles in Evanston at Northwestern, and the city has represented some interesting milestones the past few years. Most notably, he returned Thursday with a chance to be the starting quarterback for the defending world champions.

Peyton Manning is done. Brock Osweiler felt disrespected and walked. Now it’s down to Mark Sanchez vs. Siemien, the former fifth pick in the draft vs. the former 250th pick in the draft.

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Whoever wins, their job will be to play safe, smart football. That much is clear to both.

“We’re on a pretty good team,” Siemian said, who was spurred on by a nice cheering section in the Soldier Field stands with family and friends in attendance for the Broncos’ preseason debut against the Chicago Bears. “Whoever is pulling the trigger, guys are going to step up and make plays, so we just have to operate.”

Sanchez and Siemian have ping-ponged in practice and, according to reports, each has appeared to be the best option at one point so far. Sanchez started Thursday and played three series. Siemian played out the string for the first half in a total of four series. First-round pick Paxton Lynch, who has been running a clear third in the pecking order this offseason, got mop-up duty in the second half.

All three acquitted themselves well in the Broncos’ 22-0 win. The betting money might be on Sanchez, who led the only TD drive, but Siemian did enough to keep pace.

“I think as a group it was a good step,” Broncos head coach Gary Kubiak said. “I think they went out and played like they’ve been practicing. They’ve been pretty solid.”

Sanchez fired the first salvo Thursday by connecting on 7 of 8 passes for 83 yards on the opening drive of the game, including a 32-yard TD pass to Demaryius Thomas. The pass had just enough on it after Danny Travathan crushed Sanchez on a blitz and Bears corner Bryce Callahan misplayed the ball like he thought he had deep help.

“At that point [when he threw the ball], DT is still running with the guy,” Sanchez said. “But I knew before the snap, they’re bringing the pressure. At first I was going to change the protection, but nothing we could have done would have blocked that pressure. We didn’t have anything that was going to pick that up.

“So I was just going to have to stand in there and take a shot and give DT a chance. It was a pretty good shot on me. But DT did a good job getting open and finding the ball.”

But then Sanchez gave one right back. After a Bears punt, Sanchez missed an open Emmanuel Sanders and his underthrown pass was tipped by Callahan and intercepted by linebacker Jerrell Freeman. Had Sanchez put more air under the pass, it might have been a big gain.

Siemian came in and led field-goal drives on two of his first three drives. He showed good touch and patience and better arm strength than he was known for at Northwestern. That muscle was on display on his first completion of the day to Cody Latimer and on a well-thrown back shoulder throw to Benny Fowler in the red zone.

What you liked: Siemian looked the part. What you didn’t: Siemian’s 0-for-3 passing in the red zone.

“I think any time you get down there, you want to finish,” Siemian said. “I would’ve liked to finish a couple of those drives, but I’ll look back at it and see if I could’ve done a few things differently.”

Fowler put it on himself. “I had the ball. The throw was good by Trevor. The DB just made a good play,” he said.

Siemian also put the Broncos in position for what should have been a third field goal, hitting completions of 6 and 22 yards, but the kick was blocked as time ran out in the first half. The 22-yarder to Taylor was a pretty strike in which after Siemian was flushed from the pocket, he implored Taylor to come back to the ball. Siemian hit him in stride right on the sideline with five seconds left before halftime.

“We’ve built that chemistry in practice,” Taylor said. “It’s an off-schedule play, and I just wanted to make sure I stayed in bounds for him and catch the ball. He made a nice play getting away [from pressure] and getting it to me on a line.”

The race remains open for Denver’s No. 1 QB spot after one game. Sanchez finished 10-of-13 for 99 yards with a TD and an interception. Siemian was 7-of-12 for 88 yards and the two scoring drives. Lynch finished 6-of-7 for 74 yards with three sacks against the Bears’ scrub defenders.

Kubiak said he wasn’t sure how he’d divvy up the reps next week — one that features two joint practices against the San Francisco 49ers, plus a preseason game Saturday — or whether he’d flip the order and have Siemian start. But he made one interesting observation about an edge Siemian has now.

“Trevor is in command of what we do. He’s probably in the best command [of all the quarterbacks], in all honesty, just because Mark continues to learn our offense, and he’s done a great job,” Kubiak said. “But remember, Trevor is going on a year and a half now. Trevor is in command of what we do, how we do it, what we want to get done. He just needs to play. Obviously, he hasn’t played as much football as Mark has. Trevor is becoming a pro and he has a lot of confidence in himself. You see it every day in this competition.”

That’s a strong show of support for Siemian. Is this real life?

Siemian was the Big Ten’s 11th-rated passer in 2014. He had more interceptions (11) than touchdown passes (seven) that season. Siemian was even a lower-rated passer that season than Michigan’s Devin Gardner, who was benched midseason that year and was cut by two NFL teams as a wide receiver before the start of training camp last year.

Siemian’s career totals in college (27 TDs, 24 INTs, 58.9 completion percentage) were not much more impressive either. In 44 career games, he had only three games with more than 276 yards and two games with more than two TD passes. That’s why when he was taken with the 250th pick in the 2015 draft — six slots away from Mr. Irrelevant — it was still considered a surprise. (Siemian, of course, was not in town for the draft. He said he was back home in Florida because he didn’t expect to hear his name called.)

Northwestern hasn’t been a quarterback factory. Brett Basanez and Mike Kafka got cups of coffee in the past decade, but otherwise the past 60 years since Otto Graham left the NFL have not been kind to Wildcats quarterbacks. The last Northwestern QB to start an NFL game? That would be Randy Dean for the New York Giants, in 1979. Spoiler: It didn’t turn out too well.

But Broncos general manager John Elway and QBs coach Greg Knapp were impressed with Siemian’s technique and toughness, both of which were on display in a 43-40 overtime win at Notre Dame. Siemien led the upset by running for the game-tying touchdown to force OT.

One week later everything changed. Siemian tore his ACL on Nov. 22, 2014 against Purdue, an injury that many felt might end his football career. Exactly one year later to the day, he arrived here in a Week 11 game against the Bears as the one-snap-away-from playing backup to Osweiler after Manning went down with a foot injury.

Now, 235 days after taking his one and only regular-season NFL snap (an end-of-half kneeldown against the Pittsburgh Steelers), Siemian has a legitimate shot to win the job. Even he admits that he has come so far in such a short period of time.

“Quite a ways, no doubt,” Siemian said. “But so much has happened, I’ve tried to stay pretty focused and keep my nose to the grindstone. To be honest with you, I haven’t picked my head up and looked around and kind of realized what’s going on. [I’ve been] pretty focused the last year or so.”

Whoever wins the battle will have the benefit of a defense that looked dominant even without Von Miller, Demarcus Ware, Aqib Talib and Chris Harris Jr. starting. The Broncos were flying around defensively, appearing to pick up in this game right where they left off following the Super Bowl.

This team might not have improved in the offseason, but the first sample of the quarterback play was mostly good. It wasn’t long ago that we felt Manning could cost the Broncos a chance to win it all and that Osweiler might struggle in his place. They’re gone, but their replacements are off to a solid start.

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Eric Edholm is a writer for Shutdown Corner on Yahoo Sports. Have a tip? Email him at edholm@yahoo-inc.com or follow him on Twitter!

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