By Chris Emma–

LAKE FOREST, Ill. (CBS) – Control what you can control is the message that Mike Glennon and Mitchell Trubisky of the Bears are both carrying into what seems to be an impending quarterback competition.

READ MORE: Two Teens Charged In Clearing Carjacking

Glennon knew this was all possible back in late April when he sat at the Bears’ official draft party and watched the team select Trubisky second overall, and Trubisky knew his opportunity would come when he proved he was ready.

Here we are now less than two weeks from preparation for Week 1 of the regular season, and the Bears have opened the door for a quarterback controversy. Trubisky is taking some reps with the first-team offense once promised to Glennon.

“I’ve learned that continuing to control what you can control — and going back to that saying, I’m going to say that a lot — stick to that, because that’s what’s got me this far,” Trubisky said Wednesday after working with the first string for the first time.

Added Glennon: “I just have to control what I can control, and that’s going out there and playing good football for the Bears. That’s really all that came to my mind.”

Bears coach John Fox wouldn’t say whether his team is now engaged in a quarterback battle, but ultimately that doesn’t matter. This step that began Wednesday is more than just an evaluation of Trubisky, who has impressed ever since arriving in Chicago. It’s the end of the Bears’ firmly stated plan for Glennon to start in 2017 and for Trubisky to develop off to the side.

Essentially, the Bears have started the clock for Trubisky to replace Glennon.

That’s not likely to occur Week 1 as the Bears square off with the defending NFC champion Atlanta Falcons. Fox admitted that Glennon working the first half of Sunday’s third preseason game is a strong indicator he’s the starting quarterback for the opener, but it’s only a matter of time.

Ever since selecting Trubisky, the Bears have gone out of their way to ensure that the 27-year-old Glennon knew he would be the starter for 2017 after he signed a three-year, $45-million deal with $18.5 million guaranteed. The team invested in him believing he could prove to be a capable NFL starter in Chicago.

READ MORE: Chicago Weather: Weekend Warmup Continues

But Glennon also had a good knowledge of what could be coming with the Bears. Entering the free agent waters, Glennon conducted an extensive evaluation of potential suitors and their future at quarterback. He surely didn’t have to look far to find that the Bears had planned to select a developmental quarterback. Unfortunately for Glennon, his play through two preseason games hasn’t helped his case to be the starter. If anything, it may have opened up the competition.

Glennon maintains that he doesn’t feel this is a quarterback battle, but he did concede this feels all too familiar. A young and highly regarded quarterback is breathing down his neck, just like Jameis Winston did in Tampa Bay.

“I mean, déjà vu,” Glennon said. “Again, it’s situations that I’ve been through before that I handled myself well in the past, and I’ll continue to do that in his situation. “

Confidence seems to be sliding away from Glennon each day as he struggles alongside a poised Trubisky. He admitted that this new situation will provide another challenge to his place as the starting quarterback. How Glennon responds to this will define his place with this team and in this league.

Meanwhile, Trubisky has looked far ahead of the curve throughout this preseason. Not only has he shown the natural talents the Bears identified in the pre-draft evaluation, but Trubisky has also commanded the huddle and shown he’s ready to lead an NFL offense.

Glennon can stay on as the starter by showing the ability to consistently lead the offense to points — something that has to start Sunday in Tennessee. But the clock is ticking on Glennon. He may not earn a say in holding down the job.

Wednesday marked the first day that the Bears opened the door to a quarterback controversy. Even if Fox’s intention was to downplay this, the fact is that the rising rookie has pressed the unproven veteran and earned reps in his starting place.

A constant evaluation of Trubisky to Glennon is now underway at Halas Hall.

“You’ve got to earn a spot,” Trubisky said. “Every spot is earned.”

MORE NEWS: At Least 10 Shot, 1 Killed In Weekend Violence In Chicago

Chris Emma covers the Bears, Chicago’s sports scene and more for Follow him on Twitter @CEmma670 and like his Facebook page.