PITTSBURGH — A season beyond explanation for the Chicago Bears and the Pittsburgh Steelers has come down to a game that, fittingly enough, seems to have generated totally illogical rationalization.

The Bears (9-3), arguably the surprise team of the NFL season with eight consecutive victories behind a rookie quarterback whose production is meager at best, couldn't possibly have been expected to be this good so late in the season.

The Steelers (7-5), on the verge of a huge disappointment after advancing to the AFC title game in 2004 and starting 7-2 this year, couldn't possibly have been expected to be this bad so late in the season. They've lost three in a row and are in danger of disappearing from playoff contention with another loss.

Asked how the Steelers' confidence is holding up after a 38-31 home-field loss to Cincinnati left them two games out of the AFC North lead with four to play, Alan Faneca offered this candid assessment: "It's wavering."

So why then, in a game that could validate the Bears' ascension to NFC contender and all but eliminate the Steelers from the AFC playoffs, are the Steelers solid favorites?

To Bears coach Lovie Smith, the answer is simple: Despite a defense so good it's being compared to that of the 1985 Bears for its dominating excellence, there still seems to be plenty of doubt whether these Bears are for real.

"The first knock on us was we hadn't played anybody good," Smith said. "So we beat Carolina at home. Then it was that we haven't beaten anybody on the road. So we go and beat Tampa. I don't know what they're going to say now, that we haven't beaten a playoff team from last year on the road? Whatever people say is fine with us. We like being the underdog."

Given the Steelers' problems at home, the Bears might be glad they're playing in Pittsburgh for the first time since 1998. Amid numerous injuries and a big falloff in their running game, the Steelers have lost three of their last five home games after going 8-0 here last season.

Even after losing to the Ravens and Colts in succession, the Steelers had a chance to tie Cincinnati for the division lead last week. But three interceptions by Ben Roethlisberger and a rare Hines Ward fumble led to a loss that means the Steelers' only realistic chance for the playoffs, barring a Bengals collapse, is as a wild card.

To Roethlisberger, the Steelers can't afford to be thinking about last week and the chance they missed when they play the Bears, who are allowing a league-low 10.6 points per game.

"We have to have a high confidence level, because if we don't, we'll just get run over," said Roethlisberger, who passed for a career-high 386 yards against Cincinnati despite a badly injured right thumb.

What the Steelers aren't running over are opposing defenses. A year after they ran the ball more than any NFL team in 20 years, their running game hasn't generated 100 yards in any game the last three weeks, much less a 100-yard rusher.

If the Bears can shut down Willie Parker, Duce Staley and Jerome Bettis the way the Ravens, Colts and Bengals did, Roethlisberger knows the Bears' defense will start coming after him on nearly every play.

"We need to come out and play as good as we are," Roethlisberger said.

Roethlisberger, 13-0 as a rookie starter last year, can appreciate what Bears rookie Kyle Orton is going through during the Bears' winning streak. But while Roethlisberger was a major contributor to the Steelers' 15-1 record last season, Orton is seen as a caretaker who is merely along for the ride on a team winning with defense.

Orton has thrown 13 interceptions and only nine touchdown passes, and his passer rating of 60.2 isn't among the league's top 30. What offense the Bears are generating, and it's not much considering they've been held below 20 points six times during their winning streak, is coming mostly from 1,000-yard rusher Thomas Jones.

The Bears spent millions on receiver Muhsin Muhammad, but he was held without a catch in a 19-7 victory over the Packers last week.

Despite the Bears' offensive problems, coach Bill Cowher said the Steelers can't copy what other teams have done successfully against the Chicago defense because he hasn't seen any offense do much yet.

"It's pretty impressive watching them," he said.

Still Ward said even an early 3-0 or 7-0 lead could give the Steelers all the confidence they need to end Chicago's streak and right their own season before it's too late.

"They haven't played from behind," he said. "For us, it's about getting out and jumping on them early and seeing if their offense can put up some numbers."