OAKLAND — Of all the changes Jeff Garcia has faced since signing a one-year contract with the Oakland Raiders in the offseason, accepting a job as quarterback JaMarcus Russell’s backup has been the most challenging.

In addition to the usual adjustments of learning a new offense, Garcia — who has 116 career starts in 10 NFL seasons— has had to wrestle with the idea of being a reserve.

“It’s not an easy role to accept because of the competitive nature that is within me,” Garcia said Saturday in between practices at the Raiders’ mandatory minicamp. “I struggled with it when I was in Philadelphia. I had a hard time just sitting on the sideline watching.”

Russell, the No. 1 overall pick in the 2007 draft, is the unquestioned starter in Oakland but is already beginning to feel the pressure after leading the Raiders to a 5-11 finish last year while throwing 13 touchdowns and seven interceptions.

At the NFL owners meetings in March, coach Tom Cable told reporters Russell needed to take on more of a leadership role with the team and made veiled references to Russell’s work ethic.

Adding Garcia, the Raiders hope, will help Russell.

Still, the role of mentor is a new one for the 39-year-old Garcia, who played his first NFL game in 1999 when Russell was still a high school freshman.

“It’s about understanding your role and I understand what I have come into with this team,” said Garcia, who has passed for more than 25,000 yards in his career. “I understand that JaMarcus is the starting quarterback. I do believe that I am a starting quarterback, as far as caliber is concerned. Hopefully by the example that I set ... JaMarcus can see and understand that this is why I’ve been able to play this game so long and why I’ve been able to have the success that I’ve had.

“Hopefully that competitive drive is just what allows JaMarcus to increase his own competitive spirit. The greatest understanding that needs to come out of all this is that this is a small window in our lives. It’s a small window of opportunity to and to make the most of this opportunity.”

While with Philadelphia in 2006, Garcia came off the bench and led the Eagles to five straight wins in December and a spot in the playoffs. He did it despite a growing uneasiness over his situation as the backup to starter Donovan McNabb.

“That didn’t mean that I was a negative distraction to the team,” Garcia said. “I still tried to be whatever I needed to be for Donovan, which is what I’ll be here for JaMarcus. But deep inside we’re all competitors and we all play this game to be on the field, to not be on the sidelines.”

His biggest contribution, though, may come in the meeting rooms where Oakland hopes Garcia’s attention to detail will rub off on Russell in camp and throughout the season.

“He brings a lot,” Russell said. “He’s a good people person. He’s got good people skills on and off the field. I just sit and watch and admire what he does.”

Cable likes what he has seen so far from his top two quarterbacks.

“What I see out there is two guys that are trying to learn some new things and trying to get their feet settled where they need to be in terms of understanding and all that,” Cable said.

“That relationship I think is really good. It has been good in the meetings and all that. Jeff has a purpose for why he is here and I think he has embraced that.”