Ron Rivera concerned about Mike Martz

San Diego Chargers defensive coordinator Ron Rivera has been doing his homework on Mike Martz, and the study sessions have given him pause about Martz's first game as the Chicago Bears offensive coordinator on Saturday.

"We went back and we watched Coach Martz's offense and things he had done in the past," Rivera said Friday on "The Waddle & Silvy Show" on ESPN 1000. "We looked at some [film] later on San Francisco stuff where they started to get explosive down the end of the 2008 season.

"Really saw some things that were, I don't want to say scary, but it causes a little bit of concern because of how they attacked vertically."

Rivera, who was the Bears defensive coordinator from 2004 to 2006, understands the danger of attacking the wide-open system.

"If you're playing coverage, you got to be over the top of everybody because if the quarterback hits the guy running down the seam, it's going to be a big play," he said. "If you bring pressure, you got to make sure somebody is running with everybody else, or it's a big play. There is some concern because its an explosive offense."

Rivera is more familiar with Bears quarterback Jay Cutler, who played for the Denver Broncos before joining the Bears last season.

"A few years ago we were playing against Jay Cutler, who we thought, and I still think is a young, dynamic quarterback because he's got a live arm, he's athletic and mobile," Rivera said.

Rivera is glad to see the return of linebacker Brian Urlacher, who led Rivera's defense to Super Bowl XLI.

"Brian is good young man," Rivera said. "I hope he does come back, has a great season and I hope he is a Pro Bowl player.

"Brian is a different kind of animal there. He's a big athletic, physical player. He's also a very smart player."