Sunday, former Northwestern quarterback Trevor Siemian made his NFL debut with the Denver Broncos. With future Hall of Famer Peyton Manning hurt, Brock Osweiler was the starter and Siemian was his backup. Osweiler got hurt in the second quarter, and the Broncos turned to Siemian.

To Broncos fans, the debut was lost in the shuffle: Osweiler came back in the second half of Denver's 34-27 loss, a critical defeat as the team tries to hang on to its AFC West lead. But to Northwestern fans, it was big: This was the first NFL playing time by a Northwestern quarterback since Jan. 1, 2012, when Mike Kafka played his last of four games with the Philadelphia Eagles.

So we had to do a complete, comprehensive analysis of Siemian's debut. We broke down every snap Siemian played Sunday, and found some good things and found some bad things. Let's take a look:

HIGHLIGHTS

No surprises here. There was one play that was clearly the best play Siemian made Sunday:

Trevor went in and executed the QB kneel absolutely perfectly. Manning might be hurt, but even in his prime he couldn't run the QB kneel better than Siemian did here. It's clear the rookie hasn't been wasting his time on the sidelines with the clipboard. He's been studying up, making sure he knows the playbook inside and out. That showed here.

Plus, Siemian showed some qualities any coach would love to see in their quarterback. It's clear ball security is a priority for Siemian, who smartly keeps himself out of harm's way to avoid taking a dangerous hit or perhaps even fumbling the ball. And he showed his awareness of the game scenario by not trying to force anything with just two seconds before the half.

Some NFL veterans struggle to know when they should and shouldn't force things. That Siemian has such a solid grasp on the game as a rookie speaks to his intelligence -- and in many ways, it speaks to the way he was developed through Northwestern's program.

LOWLIGHTS

I think you guys know which play I'm going to bring up here. If you were watching Sunday, this play will make you cringe.

Trevor, what are you doing! There's nobody near you. Why would you willingly take a loss on the play?

I'm not going to be too harsh on Siemian. This is the type of thing that happens to quarterbacks in their NFL debuts all the time. You spend your whole life playing this game, hours and hours practicing and practicing every possible skill. And then, your first time in front of all those fans on that big stage, you freak out. Your brain turns to mush, your arm turns to flubber, and all those finely tuned skills vanish.

Siemian wasn't the most graceful quarterback in college -- far from it -- but I think we watched him enough to know that a gaffe this gauche is atypical. Let's chalk this one up to panic under the bright lights and pretend it never happened. Hopefully, Siemian can do the same. The worst case scenario is he can't clear his head and never gets past his rookie mistake.

SHOWING OFF THE SKILLS

I watched every snap Siemian took, and although this one might fly under the radar, it's the play that stood out most to me as one where Siemian showed his potential:

Is this the flashiest play? No. But Siemian's footwork is impeccable. Look at the ease with which he makes his steps.

A lot of times, you'll see a rookie QB thinking instead of doing. You don't have time to do that in the NFL. Siemian's clearly practiced to the point where he doesn't have to think.

Plus -- jokes about his 4.38 speed aside -- Siemian shows great agility here. Remember, speed and agility are different things, and both help.

ROOM FOR IMPROVEMENT

Watching the tape, I saw one play that I know Siemian's coaches are gonna show him over and over in the film room this week. Was it the worst play the Broncos ran all day? No. But when you look at what might've been, you'll see what I mean.

To understand what I'm talking about here, let's look at how the Steelers line up before the snap:

Ummmm, Trevor, look up: The Steelers are overloading your right side... and you don't have any players on the right side. That means that somewhere, somebody's going to be unguarded.

But it gets worse. As soon as Siemian snaps the ball, Pittsburgh's left inside linebacker, Terence Garvin, immediately begins running towards the right sideline.

It's clear that Pittsburgh was suspecting something to the right side of the field. If Siemian audibles to a play to the left -- maybe even as simple as a power run to the left side -- Denver's going to have a numbers advantage, and Pittsburgh might not be able to do anything about it until there's a man in the end zone.

A veteran QB probably makes these reads and subsequent adjustments immediately. Siemian just isn't there yet. It's clear that he needs more reps.

This play didn't go as well as it could've Sunday, but if Siemian and the Broncos coaching staff make sure he knows what he did wrong here, we won't see him making these mistakes for long.

* * *

Sunday, Siemian showed he has everything you need to play quarterback in the NFL: arms, legs, a uniform, a contract with an NFL team, and perhaps most importantly, one of those little pouches that you can put your hands in during the game. When the coaches called his name, he was ready. I think it's safe to say that at this point, Trevor Siemian now has an NFL career.