Jim Harbaugh and Pete Carroll don't agree on much. But they both are big fans of Marc Trestman.

The rival coaches have individual histories with the new Bears coach. Carroll and Trestman were assistant coaches under Bud Grant with the Minnesota Vikings in 1985-86 and coordinators for San Francisco 49ers head coach George Seifert in 1995-96.

At both places, they were on opposite sides of the ball. But Trestman was a mentor for Harbaugh when they were assistant coaches under Bill Callahan with the Oakland Raiders in 2002-03. Trestman was the offensive coordinator and Harbaugh an offensive assistant in his first NFL coaching job.

''He made a life-long impression on me,'' Harbaugh said Friday at the NFL Scouting Combine in Indianapolis. ''I really felt, in a lot of ways, trained by Marc Trestman. And also Bill Callahan. I assisted Marc. Marc was the coach on the staff. I was the assistant to the assistant.

With Trestman and Harbaugh as coaches, Raiders quarterback Rich Gannon was the NFL's MVP in 2002 and led the Raiders to the Super Bowl. The Raiders didn't fare as well the following season, but Harbaugh still learned a lot from Trestman.

''I continue to use his system that we learned under him and it's been very good for us. We've had a good track record,'' Harbaugh said. ''A lot of his coaching points, a lot of his ideas, a lot of his teaching. I've benefitted greatly from my experience with Marc Trestman.''

Trestman shares another trait with Carroll and Harbaugh -- the ability to get through to his players. They each do it in different ways, but the effect is similar. They get more out of players than others do. Carroll said he was certain Trestman would be able to work that magic with the Bears.

''Sure he will. There's no question,'' Carroll said. ''He's been doing it for years. He just showed championship style up [in the CFL]. Marc's been a successful coordinator when he's called plays. He'll do a fine job. It will be different for Chicago. He's a different guy than Mike Ditka. Different style. But he's a great teacher and he'll do a tremendous job leading them.''

Harbaugh said Trestman has a special quality as a teacher. It works for him.

''No. 1, he's really knowledgeable. He's got tremendous experience,'' he said. ''But if I had to put one intangible -- it would just be that's he's authentic. He's genuine. All people respond to that.''