Secondary becomes primary concern

The Bears' injury-ravaged secondary is their primary concern this week against the pass-happy Detroit Lions, but a ferocious pass rush would take a lot of pressure off what might otherwise be an outmanned group.

Starting cornerbacks Charles Tillman (ankle) and Nate Vasher (groin) did not practice Thursday for the second straight day. Vasher will not play and, even though Tillman says he will, he probably won't.

That moves nickel corner Ricky Manning Jr., who covers the slot receiver in passing situations when the defense uses three cornerbacks, into the starting lineup. Rookie Trumaine McBride, a seventh-round pick from Mississippi, will start with Manning if both Tillman and Vasher are out.

The Bears' depth in the secondary will be tested even more because the Lions, who lead the NFL in passing yardage, use three or four wide receivers more often than not. So the Bears will be in a nickel defense most of the afternoon at Ford Field. In those situations, Manning will move inside to assume the nickel position, and another rookie, fifth-rounder Corey Graham from New Hampshire, will join McBride at cornerback.

At strong safety, Adam Archuleta is practicing and planning to play with a plastic cast on his broken hand.

"It's just a great opportunity to be able to just step in and help the team any way that I can," said McBride, who was tossed into the fray in the third quarter last week when Vasher was injured.

At 5-feet-9 (in his shoes) and 185 pounds (after a big dinner), McBride isn't the ideal matchup for Lions go-to guy Roy Williams, who is 6-3 and 211, or rookie Calvin Johnson, who's 6-5 and 239 but has missed practice this week with a sore back.

"The biggest (challenge) for me is size," McBride admitted. "(Williams) is a big, physical receiver. This will be a challenge just being in the game, period, but also going against a great offense. I'm going to be in the film room even more, hopefully getting ready for the game as much as I can."

Manning has some getting ready to do as well. In the past, he has struggled when asked to move outside and play on an island as a starter. He'll certainly be tested Sunday. The Lions are averaging 345 passing yards per game and chucking it an average of 46 times a game. But that could also give the Bears' defensive backs a lot of chances to come up big.

"It will be a good challenge this week because of that great offense," Manning said. "They pass the ball a lot, so there will be plenty of opportunities to make plays."

Lions quarterback Jon Kitna threw for 446 yards last week, but the Eagles sacked him nine times and picked him off once in a 56-21 victory. That's the most effective method the Bears can use to neutralize Detroit's aerial attack and its talented flock of receivers. Bears coach Lovie Smith was asked if the pass rush will take on added importance if the secondary is banged up.

"We are banged up," Smith said. "(The pass rush is) very important. It's about the pass rush for us each week. If we are a little banged up, of course, we need to get a pass rush even more so."

The Bears have applied consistent pass-rush pressure all season and are No. 8 in the league in sack percentage. They got some encouraging news Thursday afternoon when defensive end Adewale Ogunleye (hip) and defensive tackle Darwin Walker (knee) both were full participants in practice after being limited Wednesday, although tackle Tommie Harris (knee) missed practice again and isn't expected to play Sunday. Neither is linebacker Lance Briggs (hamstring).

"If a quarterback gets an awful lot of time to pass, any of the coverage that we have is going to break down," defensive coordinator Bob Babich said. "So we need to make sure that we have a good pass rush and get him to throw the ball out on time."

That would help.