KIRKLAND – It’s not so much Brian Urlacher’s imposing size, Lance Briggs’ surprising speed or Ricky Manning’s timely interceptions.

It’s not the blue-collar fans, the classic uniforms or the smoke-like breath streaming out of facemasks.

When an offense lines up against Chicago’s smothering defense, the most intimidating thing isn’t what the Bears do – but what they don’t do.

There are few adjustments and limited tricks. When the Bears line up on a Sunday afternoon – as they will this weekend against the Seattle Seahawks – they just line up and dare offenses to come at them.

“We don’t change for anyone,” said Urlacher, a 6-foot-4, 258-pound linebacker who runs like a safety. “We didn’t double (Carolina receiver) Steve Smith (in a playoff loss last season) – maybe we should have; we didn’t. We do what we do. We run some man (coverage), some zones, and blitz a little bit.

“Our defense is pretty simple when it comes down to that.”

So simple that no one’s figured out how to attack it. Chicago’s defensive package, which is based in a Cover-2 scheme much like the one Tampa Bay rode to a Super Bowl title four years ago, is effective in that it doesn’t try to do too much.

The Seahawks know this all too well, having struggled to solve the Bears’ open-book equation in a 37-6 loss on Oct. 1. Chicago didn’t trick Seattle in that game; the Bears just beat them.

“They came out and knocked us around,” Seahawks offensive tackle Walter Jones said, “and they did a good job of it.”

If there are reasons for Seattle to feel better about the rematch, it’s because of who will be in uniform for the Seahawks – and who won’t be for the Bears. Seattle played that game without star running back Shaun Alexander and tight end Jerramy Stevens, both of whom are now healthy, while Chicago has since lost defensive playmakers Tommie Harris and Mike Brown.

Harris was particularly effective in the October game, dominating left guard Floyd Womack all day long. Harris almost single-handedly shut down Seattle’s running game, and sacked quarterback Matt Hasselbeck twice. He’s out for the year with a torn hamstring, so that gives the Seahawks one less worry heading into Sunday’s game.

“Tommie is not a good player; Tommie is a great player,” Bears coach Lovie Smith said this week, “I think as good as there is in the league at his position.

“We had him, now we don’t. No one else has a player like Tommie, but we have other good football players. We have moved on.”

Brown, who had five solo tackles in the first Seattle game, has been on injured reserve since Oct. 19 after suffering a foot injury.

Without Harris and Brown, the Bears’ defense has struggled down the stretch. After allowing 251.8 yards per game through the first 11 weeks, Chicago gave up 364.7over the final six.

Meanwhile, the Seahawks’ offense has shown some signs of coming out of its season-long funk. Alexander has only recently started to look like himself after missing six games in October and November with a broken bone in his left foot. While he might not have made much of a difference in the earlier meeting – the Seahawks fell behind 20-3 in the second quarter – the addition of last season’s NFL MVP has its benefits.

Stevens could provide a boost in that he had his best game of the season last Saturday. His five-catch, two-touchdown performance served notice that he can be a postseason playmaker.

“With Jerramy and me in, it gives us a great chance to score more first downs and also move the ball in the red zone a little bit easier,” Alexander said Thursday. “Hopefully it goes well for us.”

The general belief is that the best way to play a Cover-2 system is to send a tight end over the middle, but Urlacher’s speed makes that easier said than done.

“If he’s around the middle of the field and if we’re in Cover-2, he’ll be my responsibility sometimes,” Urlacher said. “It’s hard to say because I hardly ever get stuck on tight ends. There are times. I think the first game they tried to run the tight end down the middle one time.”

The Seahawks aren’t giving any hints about what they’ll try to do this time. Their offensive game plan is shrouded in secrecy, while the Bears’ defensive strategy is right there for everyone to see.

“You have to respect it anytime a team feels like it can just line up and play their scheme,” Seahawks fullback Mack Strong said. “They don’t feel like they have to resort to a whole lot of blitzing. They might mix stuff in every now and then, but for the most part, these guys know their role on the defense and they play it to a T.”

Notes: A veteran cornerback was at the Seahawks’ practice facility on Thursday, but it wasn’t to help out Seattle’s injury-ravaged defense. Washington Redskins cornerback Shawn Springs stopped by while visiting Seattle to tend to a business matter. … Wide receiver Darrell Jackson (toe) missed practice again Thursday but could be on the field today. He is listed as “questionable” for Sunday’s game at Chicago.