By Chris Emma—

(CBS) With rookie Mitchell Trubisky breathing down his neck, Mike Glennon revealed himself Sunday as the Bears’ starting quarterback entering this season.

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Facing plenty of pressure to hold down his job, Glennon responded well in the dress rehersal preseason game. He led a 15-play, 96-yard drive to the end zone to open his afternoon in Tennessee and paced the offense well during the first half of the Bears’ 19-7 win over the Titans. The Bears have stood by Glennon as their starter, and he stated his case Sunday as the guy.

Glennon finished 11-of-18 for 134 yards and a touchdown. More importantly, he led the Bears to 15 first downs and managed 5-of-8 on third-down conversions. After struggling his first two preseason games, Glennon proved capable of driving the offense downfield.

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The Bears created an apparent quarterback competition last week by elevating Trubisky up to the first-team offense for reps. It’s the next part of his development process but also opened up a can of worms. Glennon has now been pressed to hold down his starting job.

Trubisky took over for Glennon in the second half, going 10-of-15 for 128 yards and a touchdown. His day was highlighted by a beautiful 45-yard touchdown strike to Tanner Gentry but also brought struggles with the first-team offense. His command of the huddle wasn’t as sharp Sunday, bringing a timeout as the play clock expired and later a delay-of-game penalty on fourth-and-1.

Trubisky looked again to be everything the Bears could hope, but his development is still taking place. That’s where Glennon comes into play.

Though most of Chicago is ready for Mitch-a-palooza, Glennon is an important asset to this organization. Rather than signing a low-cost veteran placeholder to bide time for Trubisky — passing on a veteran bridge like Brian Hoyer — the Bears instead gave Glennon starter’s money with a three-year, $45-million deal with $18.5 million guaranteed. It’s because the team believes in him.

The Bears want Glennon to prove himself to be a starting quarterback this season. If that wish comes to fruition, they could then move Glennon for the kind of return an starting quarterback warrants. After all, quality starters are rarely found outside of the draft, and the Bears believe they have one in Glennon.

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Transitioning from Glennon to Trubisky was never going to be an easy process. It’s something the Bears knew well and have anticipated since making the bold second selection in April.

Once the Bears do decide to make Trubisky their starter, they’re ending their investment in Glennon. That’s why the organization is giving Glennon his chance to open the season.

Glennon made more strides in Sunday’s win and solidified his place to start the regular season.

Extra points

— The Bears were bit badly by the injury bug in Sunday’s game. Receiver Cam Meredith suffered a gruesome left knee injury that the team fears is a torn ACL. Meredith was carted off the field with his leg in an air cast. Cornerback Prince Amukamara suffered an ankle injury on the first play of the game, linebacker Leonard Floyd left with a foot injury, linebacker Dan Skuta suffered a concussion and long snapper Patrick Scales left with a knee injury.

— With the injury to Meredith, the Bears will be looking for help at receiver. There could be a place waiting for the undrafted Gentry, who hauled in the long touchdown from Trubisky. Gentry has played a role in special teams as the Bears continue to prepare him for their active roster. If they were to put him on the practice squad, an outside team would likely poach him away. Gentry could see an increased role coming with the Bears after the unfortunate injury to Meredith.

— The Bears’ plan at quarterback on Sunday didn’t include veteran backup Mark Sanchez, the only quarterback not to take the field. Sanchez has been stated as the team’s No. 2 quarterback, but that place is now in question as Trubisky rises up the depth chart. If Glennon were to become unavailable, the Bears may go straight to Trubisky instead of Sanchez. It’s something to decide in the coming weeks before the regular-season opener.

— Veteran defensive lineman Jaye Howard was ejected from the game for throwing a punch in the first quarter of the game. With that came increased opportunity for Roy Robertson-Harris, who has continued to impress in his move to the defensive line. Robertson-Harris also blocked a punt in his new special teams role, a play that resulted in a safety.

— After working in a full game-week schedule, the Bears will work in an abbreviated schedule ahead of Thursday’s preseason finale against the Browns at Soldier Field. There’s one week until the 53-man roster is set and two weeks until the regular-season opener against the Falcons.

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