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Tommie Harris: Week 13, Tommie Harris goes down with what later is diagnosed as a torn left hamstring that lands him on the IR. Week 14, the wheels begin to come off the Bears' vaunted defense. The Orlando Pace-less St. Louis Rams, amidst floundering to another disappointing finish to the season, put up 433 net yards while averaging 4.6 per carry on the ground. Week 15, Tim Rattay and Bruce Gradowski of the hapless Tampa Bay Buccaneers pounce on the Bears for 305 yards and three TDs in a surprising shootout at Soldier Field. Week 16, YIKE favorite Jon Kitna tallies 283 yards and three TDs while Detroit's two primary rushers (both scrubs) average five yards per carry on the ground. Week 17, as much as the Griese/Grossman hybrid at QB tried to single-handedly cede this game to Green Bay, it was not enough as the sputtering D allowed an (albeit mediocre) 285 yards and one TD to former great, Bret Favre. I'll give the Bears a mulligan on the 108 yards allowed to Ahman Green and Vernand Morency, first it was on 31 carries (or about 3.5 a carry) and second the Bears had next to nothing to play for.

Can the loss of one player really mean the systemic breakdown of an entire defense? Harris is a superlative DT that pressures the QB and tackles rushers, but it hardly seems possible that one man can have such an impact on a great defense like the Bears'. And yet -- Week 1-13: 12.0 points against per game; week 14-17: 26.3 points against per game.

While the Bears faced an easy schedule overall, the first group of games featured two top 11 offenses from the NY Giants (22.2 points per game) and NE Patriots (24.1 ppg) and an overall average of 19.7 ppg per opponent. The second group averaged 18.5 ppg; though with significant outliers in both Tampa (13.2) and St. Louis (22.9).

It's easy to see four games as a small sample size and simply discount them as an aberration, but when you realize that a football game is so frenzied and full of individual plays--198 passing and 93 rushing, or 291 total plays defended in those four games alone--that argument is weakened quite a bit. The Bears defensive struggles are very real but also very perplexing. This coming Sunday, Matt Hasselbeck--and a more talented passing offense than any of the Bears last four opponents--could just as probably light up the Bears for 300 yards in the air or misfire for 3 picks. Here are three Bears that will help decide.

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Brian Urlacher: The Cover 2 was developed by coaches Chuck Noll and Bud Carson of the dynastic `70's Pittsburgh Steelers. The original prototype for a MLB in the Cover 2 was HOFer Jack Lambert. He was fast, ferocious and could pick the ball like a DB.

Monte Kiffen, Tony Dungy, Lovie Smith, et al developed the modern day Tampa 2. The major difference between the two was an emphasis in the Tampa 2 on smaller speedier players to rush the passer on the line, and dropping the MLB deep to cover the gap between the split safeties. It wouldn't be surprising if in twenty years people refer to Urlacher as the prototype for MLB in the Tampa 2, but, then, some contemporaries would disagree.

Urlacher is subject to the polarized opinions, lofty praise and searing rebuke of a Derek Jeter. He's been on so many overrated and underrated lists it's patently absurd, and cutting through the dross to some sort of intelligent evaluation is next to impossible.

Here's what we can be sure of. Urlacher is a flyer of the highest order. The guy finds a way into the frame on almost every defensive play, though sometimes he's simply the fourth or fifth player in a pile. As the deep man in the middle he is frequently called on to cover TE's--especially on deep post routs--a job he, Lance Briggs and the entire Bears defense is mind-bendingly good at. Not only does Urlacher stop passes, but he's one of the meanest tacklers in football. Whatever problems the Bears have had defending the pass the last four games, I can assure you it's not Brian Urlacher's fault.

Adewale Ogunleye: For my money I prefer Alex Brown to the very dangerous Ogunleye, but while Brown must contend with team titan Walter Jones, Ogunleye gets Sean Locklear. Ogunleye was an undrafted free agent signed by the Miami Dolphins before the 2000 season. In 2003, his second year starting with the Fish, Ogunleye exploded for 15 sacks and 76 tackles. That's what Ogunleye does, too: explodes with a mesmerizing first step and strong upper body. He is, very unfortunately for Hawks fans, exactly the kind of speed rusher that eats Locklear for breakfast.

Considering the impotence of TEs against the Bears, and the Nigerian Royals presupposed use of Locklear as a red carpet to Hasselbeck, it would behoove Seattle to keep the TE in on max protect and let Seattle's receivers find a whole in the Bears' zone.

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Nathan Vasher: Last January's dismantling of the Bears D by definitive #1 receiver Steve Smith seems like an anachronism. That's because while the Bears were solid (8th) against opponents' #1 receivers in 2005, they've been downright bad (21st) this year. The problem for the Hawks: Of the three players who could qualify for that title, two are hurt (D.J. Hackett and Darrell Jackson) and the other (Deion Branch) has yet to really step up.

Vasher is a well rounded cornerback whose athleticism and big-play ability make him well suited for the Cover 2. Vasher is not a great cover corner. He has a reputation for biting on the double move and falling for play-action. In the game against Carolina last year Smith absolutely shredded Chicago's zones for 12 receptions/218 yards, and shed Vasher's coverage like a wet set of clothes. The Hawks have no single player of Smith's receiving ability, but with an absurd amount of depth at WR have a veritable mismatch against any DB covering them. That is, only if they are able to isolate those corners.

In two of the Bears final four games Chicago was facing a team with a Mike Martz, or a Martz-derived offense. Martz loves to use max protect and send wide receivers deep on complicated routs. If the QB is given time, this strategy is excellent at consistently beating a Cover 2 deep. The Hawks offense is much closer to Tampa Bay's, with lots of passes underneath right in the teeth of the Bears' zone. Two of Rattay's three TDs and 108 of his 268 yards came on long bombs to Joey Galloway and Ike Hilliard.

For Seattle to be successful on Sunday the Hawk's passing attack must be able to break habit and find receivers deep, because if Mike Holmgren and Hasselbeck play conservatively, balls will be tipped, receivers will be surrounded and passes will be intercepted.