The defense.

In preparing for their Sunday matchup at University of Phoenix Stadium in Glendale, both Chicago Bears coach Lovie Smith and quarterback Jay Cutler have taken note of what the Cardinals do to stop opponents.

"Aggressive bunch that has good stats to back them up," Smith said of the Cardinals.

Arizona ranks 11th in total defense, but fourth in passing yards allowed. The Cardinals' 36 sacks are tied for seventh in football, and their 22 interceptions are tops in the league.

Defensive coordinator Ray Horton's group has held elite NFL quarterbacks like Tom Brady, Aaron Rodgers and Matt Ryan to sub-par efforts, which is something Cutler has certainly taken notice of.

"Really good, really good," he said when asked what he's seen of Arizona. "Watching them on film, they throw a lot of different looks at you, they're not afraid to blitz you."

Cutler praised the Cardinals' secondary, linebackers and front four -- really the entire defense.

"So it's challenging, they're really good on third down and in the red zone and they force turnovers," he said. "All the things you want out of a defense."

Cutler comes into the game completing 60-percent of his passes with 17 touchdowns and 14 interceptions. He's been hit a lot, though, and fumbled the ball seven times. His top target is the six-foot-four Brandon Marshall, who has already caught 107 passes for 1,398 yards and 10 touchdowns.

Marshall will be working against Cardinals cornerback Patrick Peterson, who is quickly gaining a reputation for being able to shut down the NFL's top wideouts. He helped to hold Lions star Calvin Johnson to a 10-catch, 121-yard effort in a 38-10 Arizona win last Sunday.

Peterson has intercepted seven passes this season, and has picked off one in each of the last four games.

"Good player, physical, really good ball skills, runs well, breaks on the ball well, tackles well," Cutler said of Peterson. "Brandon's had some big matchups this year, and this is going to be another big one for him."

Perhaps Cutler's coach put it best when he talked about Peterson's combination of size and speed to go along with quickness and a willingness to tackle.

"There's not much he can't do," he said.