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Nam Y. Huh, Associated Press
Kansas City Chiefs running back Thomas Jones (20) is tackled by Chicago Bears defensive end Julius Peppers (90) in the first half of an NFL football game in Chicago, Sunday, Dec. 4, 2011.

LAKE FOREST, Ill. — Figuring out what Tim Tebow might do is just one challenge facing the Chicago Bears' defense.

Getting their assignments straight, reacting to option football and not being fooled by play-action passes are all on this week's agenda for the Bears. And then when Tebow does carry, there's the even more important task of bringing down the 236-pound quarterback who has led the Broncos to five straight wins.

The Bears' defense must play well if Chicago wants to make the playoffs. With backup quarterback Caleb Hanie struggling in place of injured Jay Cutler, the Bears have dropped two straight. And now they're without running back Matt Forte (knee sprain).

At 7-5 with four to play, Brian Urlacher figures the Bears need 10 wins to be safe.