The San Francisco 49ers' multiple weapons and uncertainty at quarterback don't matter to the Bears' defense as much as stopping Frank Gore and the run game.
"At the end of the day, when you watch what they do, hands down, first thing is the run," defensive end Israel Idonije said.
"They have a serious commitment to running the ball, and they have the talent to do that. They're a very physical offense up front, and the scheme that they run has been very successful and they have the guys to do it.
"For us, our commitment as a defense is to match that physical play and to raise our level. We consider ourselves a very physical defense as well, so it's going to be a great matchup."
The 49ers are No. 1 in the NFL in rushing yards and average gain per rush, and Gore is averaging 5.4 yards per carry. Only the Minnesota Vikings' Adrian Peterson (5.8) has a higher average among player with 90 or more carries.
"He gets downhill, one cut," said Bears defensive coordinator Rod Marinelli of Gore. "Every yard he's fighting for. I mean he twists, he turns, he fights. This guy is never down."
Since he played with Jay Cutler on the Broncos from 2006-08, Brandon Marshall has played with a lot of quarterbacks in Denver and then Miami, so many that he's lost track.
"Since we left Denver, I think I've played with seven or nine different quarterbacks, so I understand how difficult it can be," he said.
"But I think Jason Campbell gives us that luxury, that comfort level of being OK when our main guy goes down.
"I'm excited and really at ease having him in our huddle because he makes it so much easier.
"Whether he's more comfortable with our tight ends or Earl (Bennett) or (Devin) Hester, it doesn't matter. We just want to win at this point. That's all it's about."
In just one season in San Francisco, linebacker Blake Costanzo became a fan favorite for his inspired special- teams play that resulted in 17 tackles.
He's looking forward to seeing some old friends Monday night, but only up to a point.
"They're your friends until you step between the lines and then they're just like football players," said Costanzo, who leads the Bears with 10 special-teams tackles.
"But I'm excited to go back there and see a lot of the guys I played with. That's my favorite part of playing football, is the guys in the locker room and forming relationships, so it's going to be fun to go back there."
Costanzo was part of the 49ers special-teams crew last season that made the third phase exciting to fans.
"It was cool," he said. "We just had a special thing going there. Instead of going to the bathroom during kickoff or punts, they were on their feet supporting us."
Henry Melton admits he enjoys his status of leading all NFC defensive tackles in fan voting for the Pro Bowl.
"I saw that on Twitter," he said. "I got a little excited, like a little kid.
"But you can't let it go to your head, and you can't get too excited about it. It is still early and there are a lot of games left to be played."