ENGLEWOOD, Colo. --It should come as no surprise that Gary Kubiak kept three quarterbacks on the 53-man roster. He carried three passers into the regular season for his last five seasons as the Houston Texans' head coach.

But when training camp began, few pundits projected the Broncos to carry three quarterbacks. And fewer knew that seventh-round pick Trevor Siemian would not only come all the way back from a torn anterior cruciate ligament suffered last November at Northwestern -- but would thrive.

"That was a concern -- how far could we go?" Head Coach Gary Kubiak said Saturday. "He worked really hard throughout the course of the summer off with the players, and when he came back, he was ready to go, and he just continued to make plays."

Siemian's inclusion on the post-preseason 53-man roster set at the 2 p.m. MDT roster deadline Saturday marked a significant accomplishment for the seventh-round pick, even though he is likely to spend the coming his months biding his time on the scout team behind perennial Pro Bowler Peyton Manning and four-year veteran backup Brock Osweiler.

Barring a calamitous set of circumstances, Siemian won't see any action this season. But he needs to continue his progress -- both in his passing and his leadership -- on the practice field.

"He's a very confident kid. There's not a throw he can't make," Kubiak said. "I think the question was how much he can handle mentally, and from what he did, how much could he progress? And he's handled that very, very well. Guys gravitate to him. You never know about leadership until a guy walks in the door, and he has shown that. Hopefully we'll continue with that."

Siemian's arm strength was evident on his Northwestern film, and once his knee healed and he incorporated Quarterbacks Coach/Passing Game Coordinator Greg Knapp's teachings into his footwork, his accuracy began to improve along with it.

"We saw the arm. There was no doubt about the arm," Kubiak said. "When you watch him throw the ball at Northwestern, in some of the wind, the trees are blowing sideways, and he's out there making throws all over the field. You knew that he had that ability.

"Now everything else, you've got to see."

And that's what the Broncos began witnessing this summer, first on the practice field, and then in the fourth quarter of the preseason opener in Seattle, where he completed five of his six passes and stabilized an offense that flailed during a fruitless third quarter.

That was Siemian's first opportunity to relay play calls in NFL nomenclature, and he wasn't fazed by it.

"He's adapted very well to the calling system, making long calls in the huddle, things that he's never been a part of," Kubiak said. It's really part of his progress, but the physical skills, we knew they were there. With the knee coming along, [it was a] project situation. We didn't know. "

Kubiak has a better idea now.

"Every time we went on the field, he found a way to make plays," Kubiak said. "He's a leader -- a very confident young man. So we feel very good about the opportunity here, and having the ability to get him that late in the draft and to have a player with that type of ability."