"Behind Enemy Lines" is a Thursday post on the Access Vikings blog. In advance of Sunday's Vikings-Chicago game, Dan Wiederer of the Star Tribune interviewed Jeff Dickerson, who covers the Bears for ESPNChicago.com. Here are three things you need to know ...

1 The Bears are who we thought they were. Or are they?

After a 51-20 destruction of Tennessee on Nov. 4, Chicago improved to 7-1 and was receiving plenty of seemingly justifiable praise as a Super Bowl front-runner. The Bears defense was legit. Their special teams were consistently delivering. And the offense seemed serviceable at the very least.

But now, Chicago has been humbled in consecutive losses to Houston and San Francisco. They have a 1-3 record against teams that currently have winning records.

"Yes, they beat Indianapolis," Dickerson said. "But they played them in Week 1 with a rookie quarterback [Andrew Luck] making his first start. So I don't really count that. The Colts were not the team then that they are now."

And in games against top competition -- at Green Bay in Week 2, vs. Houston in Week 10 and at San Francisco this past Monday -- the Bears have been outscored 68-23.

"It's justifiable to ask, are the Bears really a legitimate contender or did they get fat and happy on a very easy schedule?" Dickerson said. "We're going to find out there."

2 If a deep playoff run is going to happen, the Bears defense will propel it.

First, an attempt to explain that eye-popping takeaway figure -- at 30 and counting through 10 games.

"The Bears just expect it," Dickerson said. "And how do you really expect takeaways when so much of it is just luck and chance? But somehow they do it. And this year, I can't remember more than one or two times where they've missed an opportunity for an interception or a fumble recovery."

Cornerback Tim Jennings leads the NFL with eight interceptions. Charles Tillman has forced a league-high seven fumbles. Tillman, in his 10th season, has 36 career forced fumbles.

"I appreciate his consistency," Dickerson said. "And I admire his toughness. The way he forces fumbles, he's going to change the way the game is played on defense. The punch is going to be a bigger part of the game going forward. So you can call Tillman a trendsetter."

3 Brandon Marshall might be the Bears' first Pro Bowl receiver since Marty Booker in 2002.

The Bears traded for Marshall last March with a belief that his reunion with Jay Cutler could be fruitful and relatively drama-free. So far, so good. Marshall has 69 catches -- second best in the NFC -- for 925 yards with eight touchdowns.

Marshall's three-TD effort against Tennessee was proof of his ability to make big plays. He also had three clutch catches for 28 yards on a game-winning drive in the final minutes against Carolina in Week 8.

"He's a volatile guy and that's not going to change," Dickerson said. "When he doesn't get the ball, he's not that pleasant to be around. But on the whole, he's been terrific. He may not have great hands and will drop some passes. But he's a great receiver. He can go up and get the ball. He's a reliable playmaker. And I think the Bears are thrilled with how he's produced."