CHICAGO -- Mitch Trubisky might have created a quarterback controversy in Chicago.

Trubisky threw for 166 yards and led three scoring drives after Mike Glennon struggled, only to have the Denver Broncos score two long touchdowns in the closing minutes to beat the Bears 24-17 in the preseason opener on Thursday night.

Though the team has insisted Glennon is the starter, the prized rookie did his best to ramp up the debate.

"Our depth chart is not going to change after one game, particularly a preseason game," coach John 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, but we're not going to change a whole lot after one game."

Denver's Trevor Siemian did nothing to hurt his standing as the apparent leader for the starting quarterback job, while Paxton Lynch did little to close any ground.

"It's an ongoing battle," coach Vance Joseph said.

Kyle Sloter threw a 47-yard touchdown pass to Isaiah McKenzie with about six minutes left in the game, and De'Angelo Henderson ran for a 41-yard score with just under two minutes remaining to put the Broncos on top 24-17.

But the biggest development in this game was Trubisky showing exactly why general manager Ryan Pace traded up a spot with San Francisco to draft him with the No. 2 overall pick.

"It was important for me to not just let this moment go by," he said.

The North Carolina product completed 18 of 25 passes in his first pro appearance after making just 13 college starts.

Trubisky replaced veteran Mark Sanchez late in the second quarter and completed his first 10 passes while leading Chicago to touchdowns on his first two possessions and a field goal on the next one. That gave the Bears a 17-10 lead.

Glennon had a rough time in his first appearance for Chicago.

Signed to a three-year contract after the Bears parted with Jay Cutler, he was 2 of 8 for 20 yards with a zero QB rating. Chris Harris Jr. intercepted an overthrown pass on the game's third play from scrimmage and returned it 50 yards for a touchdown.

TRUBISKY SHINES

Things didn't get much better for Chicago's offense until Trubisky came in with 1:55 left in the half.

He completed four passes on a 50-yard drive, connecting with Victor Cruz from the 2 to cut it to 10-7 with 13 seconds left.

Trubisky then led Chicago on a 75-yard drive early in the third, going 5 for 5 for 50 yards before Benny Cunningham ran it in from the 1 to give Chicago a 14-10 lead.

STARTING STRONG

The Broncos' defense took the ball away on two of the game's first three possessions. Denver gave Joseph a win -- albeit a preseason win -- in his first game on the sideline.

As for the quarterbacks?

Siemian -- a surprise successor to Peyton Manning last season -- completed 6 of 7 passes for 51 yards and led a field-goal drive.

Lynch came on early in the second quarter and was 6 for 9 for 42 yards. He is scheduled to start next week.

QUOTABLE

Broncos: "I don't really look at it like that," Siemian said when asked if he added distance between himself and Lynch. "I did some good things. I thought Paxton did some good things."

Bears: "When you take a guy that high I immediately knew there could be something stirred up," Glennon said about a potential QB controversy. "But I'm not going to focus on the outside world, I'll focus what's going on in the locker room and the coaches."

INJURY UPDATE

Broncos: The Broncos held out five-time Pro Bowl linebacker Von Miller and were missing S T.J. Ward (hamstring), LB Todd Davis (shoulder), C Matt Paradis (hip) and RB Jamaal Charles (knee). ... DE Billy Winn left the field on a cart late in the first quarter with a right knee injury. He was at the bottom of the scrum following a Chicago running play and is scheduled for an MRI on Friday.

Bears: G Kyle Long (ankle) and LB Lamarr Houston (knee) -- both working their way back from surgery -- topped the list of players held out by Chicago. RB Jeremy Langford (ankle) was not in uniform. ... RB Ka'Deem Carey left with a quad injury.

UP NEXT

Broncos: Visit San Francisco on Aug. 19.

Bears: Visit Arizona on Aug. 19.

---

More AP NFL: www.pro32.ap.org and www.twitter.com/AP-NFL