CENTENNIAL, Colo. -- Two things happened during Trevor Siemian's final year in college that left him position to compete for a starting NFL job. He trusted his instincts, and he ended up sharing a locker room with Peyton Manning.

To understand why Siemian remains in the Broncos' quarterback competition -- he delivered his best performance of training camp on Monday -- trace his steps to Denver. As a fifth-year senior at Northwestern, Siemian blew out his left knee at Purdue on Nov. 22, 2014. A sobering reality surfaced. It was quite possible he had played his last game. Siemian considered a career in commercial real estate. He interned for a medical device sales company.

"I was kind of hedging my bets for a bit. Then it got to a point where I was like, 'Shoot, I can still play,'" Siemian said. "Mentally I knew the knee would come back at some point. I just wanted that chance to get my foot in the door. I didn't want to be that guy sitting on his porch talking about what could have been if I hadn't gotten hurt. I had to give it a go."

There were times he wondered if he made the right decision. Tepid interest surrounded his draft status. He caught a break when coach Gary Kubiak, at the time an assistant with the Baltimore Ravens, found himself watching Siemian play one morning on the TV. He liked his arm, filing his name away and referring back to it when he took over as the Broncos coach.

"He might have said something when I came here for my visit. He was probably one of the only ones who really looked at my film seeing as I didn’t get drafted until the seventh round," said Siemian with a smirk.

Siemian received some calls about signing as a free agent as the draft wore one. Cleveland, he admitted, was the only other team he visited. It would make for a fascinating story if the kid, unwanted by so many, took over for the iconic Manning. If he pulls it off -- he needs to continue to make big plays and not play it too safe -- Manning will receive some credit. Forget selling medical supplies, Siemian served an internship in the Broncos' quarterback room, gleaning info from Manning and Brock Osweiler, who signed with the Houston Texans as a free agent.

"Looking back now, you never know how it’s going to play out but I could not have gone anywhere better," said Siemian, well-liked at Northwestern for his confidence and toughness as he played through foot and ankle injuries. "I learned so much. Nowhere better than being here."

Talking to teammates, Siemian receives praise for his leadership and knowledge of the playbook. He didn't stand out the first few days in camp, completing short passes, but making scant big plays. Monday that changed with a touchdown connection to Sanders across the middle. Sanchez failed to build on his best day. He lacked the same accuracy -- he connected on nine of his last 11 passes on Sunday -- and threw a pick six in the red zone to reserve cornerback Lorenzo Doss. Kubiak went out of his way to praise rookie Paxton Lynch, who is gaining momentum, albeit with the third team.

"I think the competition is excellent. I think one thing for sure is that I think No. 12 is really stepping up," Kubiak said.

Lynch has turned heads, and, if nothing else, Kubiak's message was a reminder to Siemian and Sanchez to take nothing for granted.

"At some time somebody is going to have to take bulk of the reps. I am not trying to look too far ahead to that," Siemian said. "I want to be able to compete where I am playing well and just see where it ends up."

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