The only new starter and underclassman on Arizona football’s defense, Cam Nelson is the self-proclaimed “”baby”” of the unit.

Just don’t tell that to the guys around him.

“”He’s a good, mature athlete,”” said senior linebacker Spencer Larsen. “”He’s learning a lot and has been able to keep his head on straight and not get overwhelmed. Coming in and being a newcomer on defense is pretty intimidating, but he’s done a good job with it.””

Nelson, a strong safety, adds versatility to a defense that ranked fourth in the Pacific 10 Conference in pass defense in 2006. Appearing in all 12 games, Nelson played the corner, nickel and safety positions in the secondary, and put in time on special teams.

But as a true freshman last season, the baby admitted he still had some growing up to do.

“”I’d get mad if coach told me something that was right,”” Nelson said. “”I’d look at it as, ‘He’s being mean to me.’

“”I need to learn how to take constructive criticism and not pout like I used to.””

Through fall camp, Nelson appears to have adapted nicely to Arizona’s defensive system, and he hasn’t warranted much criticism.

He impressed his coaches by intercepting a Willie Tuitama pass during Saturday’s final fall scrimmage, leaping up in traffic and then running another 45 yards for a return.

“”He showed a lot of range,”” said defensive coordinator Mark Stoops. “”He’s got good natural instincts and a good feel for the game.””

Larsen said the thing that excited him the most about the play was that Nelson played the ball, not the player – something young safeties usually need extra time adapting to.

“”He communicates really well,”” Larsen said. “”He talks, and that’s what you need out of a safety. You need to have someone who’s not afraid of talking and communicating with everyone, because there are certain checks that you need to make and (safeties) are the ones that make them.””

Nelson also knows he has a big act to follow. His predecessor, Michael Johnson, covered a lot of ground and was considered the Wildcats’ most athletic safety last year. Scouts thought so, too, and the New York Giants selected him in the final round of the NFL draft in April.

“”It’s a hard position to play, but he’s doing it very well,”” Stoops said. “”I’m very impressed with him. I think he’s got the makeup and skills to be a great safety.

“”Playing for all the positions in the secondary already, he’s got a good feel for the game. He picks up the concepts pretty well.””

Added Nelson of Johnson: “”It’s going to be hard to fill his shoes, but if I listen to my coaches and the guys on defense, I think I have a good chance of doing it.

“”I don’t really have much to do except listen to the older guys. It’s kind of weird being the baby, but I’m adjusted to it now.””

Safety Joseph Perkins, a sophomore transfer from El Camino (Calif.) College has beencleared to practice for the Wildcats.

Two other transfers, defensive end Levar Brown and linebacker Vuna Tuihalamaka, have enrolled in junior colleges and won’t be available the entire 2007 season.

Both are going through academic problems.