Mitchell Trubisky steals the show in Bears preseason debut

CHICAGO -- Welcome to Chicago, Mitchell Trubisky.

The second overall pick didn't disappoint in his NFL debut, ramping up speculation that he could unseat starting quarterback Mike Glennon in the not-so-distant future.

Trubisky did almost everything right Thursday night -- granted, versus second- and third-teamers -- as he led the Chicago Bears to three consecutive scoring drives in a 24-17 loss to the Denver Broncos in their preseason opener.

The rookie quarterback, who completed his first 10 pass attempts, beat Denver's defense in a variety of ways. On some plays, Trubisky stood tall in the pocket to deliver the football, and on other plays, the rookie used his athleticism to roll right and find open receivers.

Maybe the most important development, though, is that Trubisky gave Bears fans a reason to feel excited. Many fans stopped showing up at Soldier Field last season as Chicago finished 3-13 and missed the playoffs for the sixth straight year.

Coach John Fox won't make a quarterback change based on one exhibition game, but there's no doubt the night belonged to Trubisky.

QB depth chart: On the other hand, Glennon's Chicago debut was forgettable. Glennon threw a pick-six to Broncos CB Chris Harris Jr. on the third play of the game and finished 2-for-8 for 20 yards. That's a 0.0 quarterback rating if you're keeping score at home. Backup Mark Sanchez played sparingly in the second quarter, going 1-for-4 for 4 yards. Then it was the Trubisky show. He finished 18-of-25 for 166 yards and one touchdown pass to veteran receiver Victor Cruz.

When it was starters vs. starters, the Bears looked...: Overmatched. At least, on offense they did. Look, the preseason is the preseason. The Bears aren't going to show anything, because honestly, the element of surprise is the best thing offensive coordinator Dowell Loggains has going for him. But the Bears made a lot of routine mistakes -- bad reads by Glennon, late delivery, penalties, batted-down passes, drops, bad snaps (more on that in a moment). That stuff needs to be cleaned up. The defense was marginally better. It was nice to see LB Leonard Floyd beat his guy around the edge and record a sack in the first quarter.

One reason to be concerned: Aside from Glennon's obvious struggles, starting center Cody Whitehair needs to work on shotgun snaps. Glennon is 6-foot-6, so there's no excuse to sail a snap over his head. Yet on Chicago's third series, Whitehair pushed a snap wide right of Glennon that Denver recovered. Whitehair also fired a snap over Glennon's head one day on the practice field in Bourbonnais, Illinois.

That guy could start: Trubisky, duh. He looked like the best quarterback on the roster in the exhibition opener. The starting job eventually will belong to Trubisky, but the Bears have preached patience. Don't expect the Bears to overreact to one preseason game, but Trubisky is now the fan favorite. The calls to start the rookie will only grow louder if Glennon and the Bears get off to a bad start in the regular season.

Rookie watch: Running back Tarik Cohen looks like a great addition to Chicago's backfield. The fourth-round pick did a little bit of everything on Thursday night -- carrying the football and returning punts on special teams. Cohen has great quickness in the open field. Chicago actually ran Cohen between the tackles a couple times versus Denver, but in the regular season, the plan is probably to get him the ball in space. Tight end Adam Shaheen was also targeted frequently in the passing game.

Special-teams sizzle: Finally, the Bears made something happen on special teams. Deonte Thompson, Eddie Jackson and Cohen all pitched in with nice returns on punts and kickoffs -- Thompson ran a kickoff back 44 yards in the first quarter. The Bears haven't made a splash on special teams since Devin Hester left town. They have to get something out of their third phase to be competitive in 2017. On the flip side, Chicago had some trouble covering kicks.