LAKE FOREST, Ill. – Chicago Bears cornerback Charles Tillman joked that he covers less ground in his car than Drew Brees does in the air.

“He’s passed for over 4,000 yards,” Tillman said. “I don’t even drive that far.”

With a win over New Orleans, Chicago would advance to its first Super Bowl in 21 years. Standing in the way is the NFL’s No. 1 offense and a quarterback who passed for a league-leading 4,418 yards during the regular season.

They have one receiver, Marques Colston, who had 1,038 yards, and three others with more than 600: Devery Henderson (745), Reggie Bush (742) and Joe Horn (679). Bush also ran for 565 yards and Deuce McAllister gained 1,057, so the Saints don’t mind handing the ball off, either.

It’s easy to see why Bears defensive coordinator Ron Rivera called them “dynamic.” Why Tillman used words like “great,” “fiery” and “explosive.”

And why cornerback Nathan Vasher said the Saints will “make due” whether or not Horn is able to return from a groin injury that kept him on the sideline the last month of the regular season and last week against Philadelphia.

“They’ve been doing a great job,” Vasher said. “I don’t know if he’s going to play or not, but we’re going to prepare like he is.”

The Bears’ defense dominated for much of the season, then seemed to take as many hits as it dished out. It went from allowing 251.8 yards through the first 10 games to 364.7 over the final six of the regular season, and its ranking dropped from first to fifth. After forcing 39 turnovers through the first 12 games, it came away with five over the next four.

That does not include last week’s 27-24 overtime victory over Seattle, in which the Bears allowed 306 yards and had one takeaway – an interception by cornerback Ricky Manning Jr.

“I think we’ve been having a conscious effort to get the ball out, but I think teams have been doing a good job of keeping it themselves,” Vasher said. “I think once you get one turnover, another one starts, and it’s like a snowball effect. That’s definitely what we’ll be trying to do this week.”

The reasons for the drop-off on defense include injuries, most notably to safety Mike Brown (foot), the leader of the secondary, and tackle Tommie Harris (hamstring). Then, tackle Tank Johnson was inactive for one game last month and suspended for another after being arrested on misdemeanor gun charges and going to a nightclub less than 48 hours later with a friend, who was shot to death.

The defensive pressure simply wasn’t there.

And in the backfield, starting cornerbacks Vasher and Tillman and backup safety Todd Johnson all missed time due to injuries late in the season. The Seattle game was the Bears’ first with Vasher and Tillman since a 10-point win over Minnesota on Dec. 3.

“We’ve been hit with everything from injuries to people saying we’re not as good to having to play from behind,” Manning said. “We’ve been tested a lot this year.”

Now, here comes a real big one – especially for the defensive backs.

The Saints led the league with 65 completions of 20 or more yards, and Brees was the NFC leader with 26 touchdown passes and a 96.2 passer rating. Bush’s 88 catches led NFL rookies and were the most by a rookie running back in league history.

The Bears ranked sixth against the run and 11th against the pass, even though they were second in the league with 24 interceptions and allowed just 37 completions for 20 or more yards – third fewest. They’re built on speed and believe they can catch a New Orleans team that, in some ways, reminds Manning of the Seahawks.

Both teams mix up formations, although the Saints show more shifts and motions and are more versatile. And their receivers will test the secondary.

“They’re great,” Tillman said. “Colston, I think he was a seventh-rounder, but he’s not playing like one; he’s playing like a first-rounder. He’s playing some good football right now. I don’t know if Joe Horn’s going to play. … He’s a Pro Bowl-caliber player.”

Tillman took a beating in last year’s playoff loss to Carolina, when Steve Smith caught 12 passes for 218 yards, but he was better last week against Seattle.

“I thought Charles played very well,” Rivera said. “Last year, a lot of people hammered him. He’s playing very well for us, very physical, very disciplined. I think he’s matured and grown.”

Manning has a history of coming up big in situations like this. As a rookie four years ago, he had three interceptions to lead the Carolina Panthers past the Philadelphia Eagles 14-3 for the NFC title. He picked off Donovan McNabb twice in the third quarter, at the Panthers 14 and then at the Eagles 37 to set up a touchdown.

“I was just being real physical with the receivers,” said Manning, who signed with the Bears as a restricted free agent last offseason.