No one's disputing that the Bears will miss eight-time Pro Bowler Brian Urlacher at middle linebacker calling defensive signals, making plays and dispensing leadership as he's done for 13 years.
"He's one of the best linebackers in the history of the game," seven-time Pro Bowl weakside linebacker Lance Briggs said of Urlacher. "When you have someone we've all been comfortable with, someone who knows how to take control, (you miss it)."
But Urlacher's replacement, Nick Roach, has started 55 games for the Bears, although only three were at middle linebacker. The others were on the strong side, where the responsibilities are different.
Still, the middle is not foreign territory to Roach.
"Plugging Nick Roach in is somewhat comforting because he's played the position, and he understands all the calls," Briggs said. "It's just (him) kind of about reinforcing his familiarity with playing the Mike (middle)."
Roach got valuable experience playing in the middle all last off-season and then through training camp and the preseason while Urlacher nursed his surgical knee back to health.
"I wish Brian was in there, obviously," Roach said. "It's unfortunate to see him go down, but I've been preparing for it for a while."
The biggest adjustment for Roach is making the defensive calls and making sure everyone is playing the right defense and is properly aligned. But that's not as formidable a task on a veteran crew like the Bears as it would be on a more inexperienced defense.
The biggest problem for Roach is that he's just not Urlacher.
"Brian is a Hall of Fame linebacker," defensive coordinator Rod Marinelli said. "He's done it for so long. But Nick has got great movement, great speed, he's been here for a long time, he understands the system, he's done it before and he's fast.
"He's a very good tackler, and he's smart. He brings a lot to the table. He's going to do a heck of a job. We feel real good about him."
The Bears are also preparing for Chicago native Kelvin Hayden to replace NFL interception leader Tim Jennings at cornerback. Jennings, whose 8 picks are 3 more than anyone else in the NFL, missed a second straight day of practice Thursday with a shoulder injury.
But, just like Roach, Hayden brings a wealth of experience, including 47 starts over the previous seven seasons. The 6-foot, 195-pound Hayden moved past D.J. Moore to become the Bears' No. 1 nickel corner four games ago.
"He's been in this system," Marinelli said. "Not just here, but in Indy. He understands the system. It's his chance to step up and really go right now. He's started in a Super Bowl and all of those things. He's going to do fine."
With Hayden replacing Jennings, Moore should be back at nickel, where he seemed to fall out of favor midway through the season.
"If your play isn't exactly what we think it should be, then you open the door for someone else to get an opportunity," coach Lovie Smith said. "Most of the time you get another chance, so what you have to do is make plays. It's as simple as that. It's all based on performance on the football field.
"D.J. is a pro. When he did take a step back, he was doing everything he possibly could behind the scenes to help this team. He's a good player. Hopefully he'll get another shot."
With backups stepping in, the task is to step up, continue the trek to the playoffs and eventually get Urlacher back in the mix.
"We're fortunate that (when) Brian went down we were 8-4 with four games to get to the playoffs," Briggs said. "It's our job now to make sure we get into the playoffs and, once we get in those playoffs, Brian will be ready and he'll come back and he'll lead us the way he always has."