By Chris Emma–

(CBS) With each passing blitz, Broncos defensive coordinator Wade Phillips must have been holding in a laugh.

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The Bears’ offensive line wasn’t ready for what was coming from the defending Super Bowl champions in their preseason opener Thursday. Teams don’t game plan much, if at all, for the first preseason game, and the Bears looked quite unprepared.

Phillips brought the heat in unexpected ways and exposed the Bears’ weaknesses on the offensive line. The Broncos beat the Bears in a 22-0 drubbing at Soldier Field.

“We didn’t execute as well as we need to or as well as we should have,” Bears coach John Fox said of the offensive line after the game. “Part of it’s recognition, getting it communicated and we didn’t do that as well as we should have.”

Come Saturday morning, the Bears had cut two young linemen and signed a pair of veterans, Khaled Holmes and Shelley Smith. A few days before, they had waived Nick Becton and signed Mike Adams, a three-year veteran with 20 starts.

Prior to training camp, the Bears had signed veteran guard Amini Silatolu, who has played in 34 games and made 28 starts.

There has been a lot of shuffling along the Bears’ offensive line since April. Chicago general manager Ryan Pace made the move to draft Cody Whitehair in the second round, willing to realign the rest of the unit around his future at left guard.

The Bears were willing to even part ways with reliable veteran Matt Slauson two days after drafting Whitehair.

The sudden retirements of Manny Ramirez and Nate Chandler created greater concerns of depth, which forced the corresponding moves to fill depth.

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When second-year center Hroniss Grasu suffered a torn ACL in training camp to end his season, the Bears had to adjust again, this time moving Ted Larsen into the role of center in a maneuver to foster Whitehair’s future at left guard.

From cutting Slauson to transitioning Larsen and adding veteran depth pieces in between, most of the Bears’ moves on the offensive line are centered around Whitehair’s future at left guard. Pace believed in the Kansas State product and was willing to rework the Bears’ plans.

The Bears’ youth on the offensive line was exposed in the preseason debut, with players like Donovan Williams, Cornelius Edison, Dan Buchholz, Martin Wallace and more combining for zero career NFL starts.

The presence of a veteran player like Slauson would’ve been a help for this team. In his absence, the Bears have with their recent flurry of moves looked to add a little more experience to their reserve unit, with 48 combined starts on the second team as an insurance policy behind Whitehair, Charles Leno and a starting group that can’t afford more attrition.

Of course, experience doesn’t necessarily mean they’re in a better position.

“Again, we’re always looking to get better,” Fox said of the most recent moves. “We’ll see how that pans out. Obviously, they’re a little behind as far as knowledge of our systems. But our coaches will work with them and hopefully get them schooled up by Thursday.”

The Bears are desperately hoping for good health on the offensive line. The same can be said for 31 other teams, but the Bears simply don’t have the depth to replace another starter. They’ve tried to secure veteran depth in case of emergency, though that’s not a promising proposition.

Coaching and preparation may help the Bears’ offensive line prevent blitzing in the aftermath of Phillips’ stunts, but that only brings the unit back to competence.

Early on, it’s apparent the Bears’ depth — or lack thereof — is a great concern moving forward.

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