Louis Riddick says Mitchell Trubisky displayed the things you want to see from a quarterback in the rookie's NFL debut. (0:38)

CHICAGO -- Bears coach John Fox said he won't change the quarterback depth chart based on rookie Mitchell Trubisky's impressive performance in Thursday's preseason opener against the Denver Broncos.

"Our depth chart is not going to change after one game," Fox said. "That's a really good defense our first unit went against, probably one of the top three defenses in the league. You have to look at a lot of different things. I can understand how you guys might think [we could make a change], but we're not going to change a whole lot after one game."

The Bears have deftly avoided any quarterback controversy between Mike Glennon and Trubisky, but the rookie's successful debut, coupled with Glennon's struggles, could make that tougher moving forward.

Glennon's career with the Bears got off to an inauspicious start. The exact opposite can be said about Trubisky's effort in Chicago's 24-17 exhibition loss at Soldier Field.

Signed in free agency to replace longtime starter Jay Cutler, Glennon threw a pick-six on the third play of the game. He fired a pass over the head of tight end Zach Miller that landed in the arms of Broncos cornerback Chris Harris Jr., who returned it 50 yards for a touchdown. Miller appeared to be triple-covered on the play.

Glennon and Chicago's offense then promptly went three-and-out on their second series. On the Bears' third offensive possession, a shotgun snap sailed high and wide right of Glennon, and Denver's Jamal Carter recovered.

Glennon finished the night 2-for-8 for 20 yards. His passer rating was 0.0.

"You kind of have to put it in perspective," Glennon said. "Like I said, we're exactly one month out [from Week 1 against the Falcons]. For me, it's just good to get back out playing. I got to get used to coming out as a starter and playing and being that guy. A couple more preseason games to tune this up and I'm confident we'll do that."

Fox said he is not worried about Glennon's confidence.

"No, not at all," Fox said.

It was a Bears debut to forget for quarterback Mike Glennon, but coach John Fox said after Thursday's game that Glennon still tops Chicago's depth chart. AP Photo/Nam Y. Huh

The second overall pick of the 2017 NFL draft, Trubisky entered the game with the offense at midfield with 1 minute, 55 seconds left before halftime. He quickly guided the offense down the field, going 4-for-4 for 24 yards, including a 2-yard touchdown toss to veteran wide receiver Victor Cruz.

Trubisky attempted two other passes on the drive that fell incomplete, but Denver's defense was penalized on both plays. He went 5-for-5 for 50 yards and led the Bears to a touchdown on his second drive as well.

He ended the night 18-of-25 for 166 yards, one touchdown and a quarterback rating of 103.1.

"I thought it was fun," Trubisky said. "That's what I wanted to do, to go out there and be consistent, move the ball on offense and be in command in the huddle and at the line of scrimmage. The offensive line did a great job taking care of me, and the running backs and receivers did a great job of catching and running with the ball. It was a good start, but we have a long ways to go."

Trubisky added: "It was important for me to not just let this moment go by and to realize how far I've come, stepping onto the field and soaking it in. This is a special night."

Veteran Mark Sanchez, Chicago's No. 2 quarterback, played sparingly in the second quarter, completing 1 of 4 pass attempts for 4 yards.