The Raiders confirmed Thursday that they have filed a grievance against former quarterback JaMarcus Russell in an effort to get back $9.55 million of the $39 million they paid him.

The Raiders say the contract was changed at one point and that he's not allowed to keep all the money he collected before his May 6 release. Oakland contends that some of the money was actually an advance on his salaries for the upcoming three seasons.

Not so, Russell's agent said.

"The money in question was fully guaranteed. That is why JaMarcus was forced to hold out and miss all of training camp as a rookie," Eric Metz told Yahoo! Sports. "The Raiders know that and this is our only comment."

Russell, the No. 1 overall pick in the 2007 NFL draft, was guaranteed $32 million as part of a six-year contract reportedly worth $68 million.

Russell will be represented in the grievance by the NFL Players Association.

One source close to Russell says the quarterback is currently in Arizona getting help losing weight. Russell, fined last season for being overweight, is looking to drop 25 pounds and get down to 260 before signing with another team.

The Raiders cut Russell after trading for Washington quarterback Jason Campbell, but they did take a chance at losing another big chunk of change by having Russell attend a minicamp. If he had gotten hurt, he would have collected an additional $6.45 million.

Oakland cut him the following week, saving that $6.45 million but still on the hook for another $3 million guaranteed for this season.

Russell, 24, completed just 52.1 percent of his passes (354 of 680) as a Raider for 4,083 yards, with 18 touchdowns and 23 interceptions in 31 games. He lost 15 of his 25 fumbles, was sacked 70 times and had a passer rating of 65.2.

E-mail Vittorio Tafur at vtafur@sfchronicle.com

This article appeared on page B - 2 of the San Francisco Chronicle