We're Black and Blue All Over:

Here's what we know: Chicago Bears linebacker Brian Urlacher suffered what initially looked like a catastrophic left knee injury in the 2011 season finale against the Minnesota Vikings. The injury was later announced as sprained medial collateral and posterior collateral ligaments, requiring no surgery.

Urlacher didn't participate in the team's on-field work during the offseason, and when he resumed practicing at the start of training camp, he was wearing a brace on the knee. Now Urlacher has missed four consecutive days because of soreness in the knee, and it's possible he won't play in the Bears' preseason opener against the Denver Broncos.

Here's what we don't know: Are the Bears merely being cautious with a veteran who really doesn't need every practice repetition in camp? Or is this an indication that Urlacher hasn't fully recovered from the original injury and could be limited when the regular season begins?

Coach Lovie Smith didn't seem concerned when speaking with reporters Sunday, and in the short term the Bears can move outside linebacker Nick Roach to Urlacher's spot in the middle. But the Bears don't have anything close to an heir apparent on their roster, as they found out when Urlacher dislocated his wrist and missed 15 games in 2009. Their defense is much different when he is not on the field.

Continuing around the NFC North:

• It's time to worry about Urlacher, writes Bob LeGere of the Daily Herald.
• The Bears were surprised by receiver Devin Thomas' decision to retire. Michael C. Wright of ESPNChicago.com has more.
• Thomas' departure opens an opportunity for second-year receiver Dane Sanzenbacher, whose chances to make the team have improved, notes Sean Jensen of the Chicago Sun-Times.
• Brad Biggs of the Chicago Tribune wonders if the Bears will trade offensive lineman Chris Williams now that appears J'Marcus Webb will win the starting left tackle job.
• The NFL's settlement talks with New Orleans Saints linebacker Jonathan Vilma could mean a reduced suspension for Green Bay Packers defensive lineman Anthony Hargrove. Chris Mortensen of ESPN has the story.
• The Packers' lack of depth at left tackle was exposed by a concussion to starter Marshall Newhouse, who did not practice Sunday night. Herb Taylor and rookie Andrew Datko got the work with the first team, according to Pete Dougherty of the Green Bay Press-Gazette.
• Nine Packers veterans were given Sunday night's practice off, notes Tyler Dunne of the Milwaukee Journal Sentinel.
• Receiver Diondre Borel made a number of notable plays Sunday night, writes Jason Wilde of ESPNMilwaukee.com.
• The fourth round of the draft was the right time to take a calculated risk on receiver Greg Childs, who will miss the season after tearing the patella tendons in both knees. Tom Pelissero of 1500ESPN.com explains.
• Jeremy Fowler of the St. Paul Pioneer Press looks at the Vikings' high number of one-year contracts.
• The Star Tribune reviews what we've learned about the Vikings' defense and special teams in camp.
• What did Detroit Lions defensive end Cliff Avril miss by not attending the first eight days of training camp? "Soreness," Avril told reporters Sunday. Maya Jones of the Detroit News has more.
• Lions receiver Nate Burleson is working on his own version of the Lambeau Leap, based on his practice work Sunday at Ford Field, writes Dave Birkett of the Detroit Free Press.
• Anwar S. Richardson of Mlive.com checks in with Lions offensive lineman Corey Hilliard, who is once again in competition for a roster spot.