Broncos head coach Gary Kubiak named the 2015 seventh-round pick his starter for Week 1 on Monday, per DenverBroncos.com's Andrew Mason:
Kubiak announced to the team Monday morning that Siemian will be the team's starting quarterback, bringing down the curtain on a competition that had been the dominant story of the offseason and training camp.
Kubiak informed Siemian, Sanchez and Paxton Lynch of his decision prior to sharing it with the entire team.
Siemian, 24, made just one appearance as a rookie—a kneel-down to end the first half in a December game against the Pittsburgh Steelers. He was otherwise relegated to the sideline as Peyton Manning and Brock Osweiler split starting duties. The NFL noted on Twitter that he's the only quarterback without a career passing attempt to take over a defending Super Bowl champion in Week 1.
According to NFL Network's James Palmer (via NFL Network's Ian Rapoport), Siemian was unsure of his football future prior to April's draft and had a job lined up outside of the league.
Sanchez appeared to be the favorite to replace Manning after the Broncos acquired him in an offseason trade with the Philadelphia Eagles. He has 72 career starts on his resume, made marked improvements in Philly after his New York Jets tenure and is no doubt the "safer" option. Given the Broncos' desire to defend their championship, Sanchez looked likely to win a preordained competition.
Siemian nonetheless had the support of Broncos coaches, who said it would be an open competition. The Northwestern product started Denver's second preseason game after Sanchez earned the nod in its exhibition opener.
Siemian seemed confident in his chances to take the starting job prior to Week 1 of the preseason, per Troy Renck of Denver7:
Absolutely, to answer the question, I think I can win the job. I am trying not to do too much. I am trying to stay within myself, and I think that's good enough. I would have not changed mindset much if I was one or two. That's one of the things out of my control. It's awesome to be up there with Mark. I think we have been pushing each other all camp.
While rookie Paxton Lynch was technically part of the quarterback competition, he's at least a year away from being a legitimate NFL starter.
Siemian started the last two preseason games, throwing for 122 yards with a touchdown and an interception in Saturday's win over the Los Angeles Rams. Kubiak spoke of being impressed with Siemian after the game, per Jeff Legwold of ESPN.com:
I'm impressed. I think he's very calm. I can tell by the way he handles the team in the huddle, he's got control of what's going on. Gets a bad break on the 'go' ball and comes right back and goes down the field. I think what I see is a guy getting better. ... I've got a lot of work to do. I'm going to make a decision this week. ... I'm going to do that, but at the same time, I've got a lot of things going on. I'll take my time and do it the right way.
Choosing Siemian is not necessarily an indictment of Sanchez. He's a known quantity at this point. The Broncos could plug him in at any point, and he's going to perform as a slightly below-average starter. There aren't any surprises.
Both Rapoport and ESPN's Adam Schefter noted the Broncos will now have to make a decision on whether to retain Sanchez:
Siemian, as he's shown in camp and the preseason, thrives on defying expectations. He may never be a star, but this show of faith could lead to at least average quarterback production. That would be an improvement from last season's dumpster fire and could lead to a more well-balanced team.
Otherwise, the Broncos may have to call upon Lynch if they cut Sanchez.