NAPA, Calif. — Oakland Raiders receiver Javon Walker reportedly told the team he wanted to retire and offered to return his $11 million signing bonus before being talked out of it by owner Al Davis.

ESPN, citing an unidentified source, reported today that Walker told the team on Thursday of his intentions to retire. Walker has been at practice the past two days and apparently has had a change of heart.

The Raiders had no immediate comment on the report and messages left with Walker and his agent were not immediately returned.

Walker's tenure with the Raiders got off to a rocky start after he signed a six-year, $55 million deal in March that included the $11 million signing bonus.

He was criticized by coach Lane Kiffin for being out of shape in offseason workouts and then was seriously injured in June during a robbery in Las Vegas.

Walker was discovered unconscious and beaten on a back street near the Las Vegas Strip following a night of partying. Walker was treated at a hospital for a concussion and facial injuries. He has declined to address the topic, saying at the start of camp that it was too soon to talk about it.

Brought to Oakland to be the team's No. 1 receiver, Walker instead has struggled in training camp and not performed nearly as well as less heralded players like Todd Watkins.

He has been limited to one practice a day because he is still recovering from a knee injury last year. Walker has struggled when he has practiced, dropping passes and having miscommunications with his quarterbacks on patterns.

Kiffin said Thursday he hoped Walker would be able to practice twice a day beginning Monday and that it would help his progress with his new team.

"There's progress being made. I wouldn't say as much as I'd like at this point so we're going to continue to push him," Kiffin said. "I think pushing him back into two-a-days will help him as well."

Walker was released by Denver in February after catching 26 passes for 287 yards and no touchdowns in eight games last season. He started the season with two 100-yard games before missing two months following a third operation on his right knee.

Coming off a torn knee ligament that wiped out most of his 2005 season in Green Bay, Walker piled up 1,084 yards and eight touchdowns on 69 catches in 2006 for Denver.

Walker made the Pro Bowl with the Packers in 2004 after catching 89 passes for 1,382 yards and 12 touchdowns. He has 252 career catches for 3,815 yards and 30 scores.

On Jan. 1, 2007, a still-unidentified gunman targeted a car carrying Walker and several Broncos teammates in a drive-by shooting outside a downtown Denver nightclub. Darrent Williams, a defensive back, died in Walker's arms in their rented limousine after an apparent altercation between a handful of athletes and other partygoers.