According to a source, Raiders owner Al Davis persuaded Walker to remain with the team.
Walker signed a six-year, $55 million deal with Oakland in the offseason after a trying 2007 marked by a knee injury.
Walker has been at practice the past two days and apparently has had a change of heart.
"That's a done issue," Walker said late Saturday following the Raiders' evening practice. "I'm not really sure what happened but that's a done issue. That's something that obviously people hear stuff. I'm here practicing, waiting, and [I] obviously can't wait till the season starts.
"I'm in a great frame of mind. Why wouldn't I [be]? I'm with a new team, a great bunch of guys. I'm looking forward to getting this season on the road and actually looking forward to going into next week and try to put everything together as a team and as an offense."
The transition has not been smooth.
He was criticized by coach Lane Kiffin for being out of shape in offseason workouts. Walker also was reportedly abducted, beaten and robbed near the Las Vegas Strip in June.
According to police, Walker was found unconscious on a side street shortly after dawn on June 16.
He was hospitalized for two days with facial injuries and a concussion and told investigators that about $3,000 in cash and $100,000 worth of jewelry were taken.
Police released a grainy surveillance videotape on June 24, identifying a man in it as a second suspect after the arrest of a first suspect.
Unlike Walker, though, the Raiders' coach isn't so sure the retirement issue is over.
"I worry a lot about it," Kiffin said. "For someone to discuss retirement, and then to come back and change his mind a day later. I'm worried a lot about it. I'm worried about where he's at mentally, because these things happen sometimes and they come back up again, because maybe they come back and maybe it isn't necessarily for the right reasons. So were going to continue to communicate with him and push him out there on the field and get him better."
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."
Chris Mortensen covers the NFL for ESPN. Information from The Associated Press
was used in this report.