ENGLEWOOD, Colo. -- Peyton Manning, who was what Denver Broncos linebacker Von Miller called "the king of studying," once offered this on defensive coordinators:

"They’re always looking at how you did things in certain situations, how you reacted to what they did, how you handled certain blitzes or certain coverages. They’re always looking for something they can take advantage of, so I always have felt like the most important thing I can do is really self-scout, make sure I’m doing everything to fix my weaknesses, work on the things I need to work on, before they take advantage of them."

And right now, personnel executives and defensive coaches from the 12 teams that remain on the Broncos' schedule are going to school on Trevor Siemian.

One thing future Broncos opponents learned about Trevor Siemian in last week's win over the Panthers: the QB likely won't lose his composure when facing a deficit. Justin Edmonds/Getty Images

Siemian introduced himself to much of the country last week in the Broncos’ 21-20 victory over the Carolina Panthers in the season opener. And while it was a tough go against a stout Panthers defense -- Siemian finished with two interceptions -- he also showed the composure that got him the starting job.

The Super Bowl rematch, after all, was the NFL’s opening night, with plenty of pomp and circumstance to go around, and the Broncos trailed 17-7 at the end of the third quarter. Siemian helped lead two scoring drives in their last three full possessions of the game (the Broncos’ last possession was a kneel-down to close things out).

"Obviously he had two decision issues that we have to clean up," coach Gary Kubiak said. "He was very calm. ... Being down 10 bothers some guys in this league. You’re going to get down in this league sometimes, but you have to maintain your composure."

Before last Thursday, Siemian’s entire NFL resume was any information folks had gleaned from his work in the preseason, watching him go through pregame warm-ups last season and his one regular-season play in 2015 -- a kneel-down to end the first half of a game against the Pittsburgh Steelers in December. That was it.

But now, at least part of Siemian’s development will hinge on how he handles the countermoves he will get from defenses. The Indianapolis Colts have a little more to work with heading into this Sunday's game than the Panthers did before the opener.

The Cincinnati Bengals will have a little more information before the Week 3 game against the Broncos, and the Tampa Bay Buccaneers will have a little more before their Week 4 meeting. And so it will go -- into November and December and, the Broncos hope, beyond.

Defensive coaches will decide what Siemian likes, what he doesn’t like, and more importantly from a defensive standpoint, the things they believe will make Siemian uncomfortable. They’ll likely start with the idea that Siemian has a rare arm, and like most quarterbacks with that kind of arm, he will believe in it too much and throw passes into places he shouldn’t.

"I think making good decisions is always a priority," Siemian said. "Doing the right thing with the ball, making the right read -- that’s always going to be something I want to do. Every possession matters; I don’t want to put us in bad situations."

And while the Colts’ secondary is currently riddled with injuries -- the Lions’ Matthew Stafford was 31-of-39 passing for 340 yards and three touchdowns against them last week -- they will likely offer Siemian some unique looks in the pass rush. Colts coach Chuck Pagano and his staff made things difficult for Manning, in that regard, over the past four seasons.

"They have a lot of things that can cause you problems as far as the pressure standpoint," Kubiak said. "Chuck is a really good coach and a heck of a defensive coach. … I have a lot of respect for [Colts defensive coordinator] Ted Monachino … and obviously this organization has had trouble with them for the last couple of years."

So as the weeks progress and the calendar gets flipped, Siemian will certainly have to study the teams that he will face, but he also will have to look at himself and try to see what defensive coaches will see.

"I trust our coaches and our game plans," Siemian said. "But I think you always have to look at what you do. That was one of the biggest things I took from Peyton -- was how, Monday through Saturday, he looked at how he thought people would come at him. And he had seen everything and still always looked at it, went over it, studied it. That was great for a player like me to see, how to do it, and why it’s important."