Oakland also waived linebacker Grant Irons and defensive end Greg Spires, and placed receiver Drew Carter, fullback Oren O'Neal and cornerback John Bowie on injured reserve with season-ending injuries. The Raiders also claimed fullback Luke Lawton off waivers and signed defensive backs Marviel Underwood and Nate Lyles.
The Raiders reduced their roster to 77 players, plus international practice squad player Mauricio Lopez, who does not count against roster limits. Oakland needs to be down to 75 players by Tuesday, and then the final cut to 53 comes Saturday.
Cooper had been a valuable special teams player in 3 1/2 seasons in Oakland, but had fallen behind rookie Tyvon Branch. Raiders spokesman John Herrera said Cooper planned to retire but hadn't filed the paperwork yet so he had to be waived. Cooper played seven years in the NFL, going to the Super Bowl with Carolina following the 2003 season.
"He came in and was just done playing and wanted to retire," coach Lane Kiffin said. "He said bye to everybody. We wish him the best. He's a really neat guy who has done a lot of things here. It may be even something that we keep him involved during the season, coming in on Wednesdays during the special teams meetings, being around the guys and working with the young guys as well."
Carter and O'Neal both went down with devastating knee injuries in the first quarter of Saturday's exhibition loss to Arizona.
That left the Raiders with converted wide receiver Marcel Reece as the only backup to Justin Griffith. They signed Lawton and then also played halfback Michael Bush at fullback in practice Monday.
Bush rushed for 2,508 yards in his college career at Louisville and was considered one of the top backs in the country before breaking his leg in September 2006. He sat out his entire rookie season and was behind Justin Fargas and Darren McFadden at halfback.
"I'm pretty sure I can take it on," Bush said. "I'm still at a point where I'm glad to be on the field anytime I can get an opportunity to play. I'm still waiting for my chance to carry the ball, as well. The more I can do the better, be a versatile player. So, that's a good thing."
Lawton was released on Saturday by Philadelphia. The Eagles acquired him in the offseason from Indianapolis for a conditional seventh-round pick.
Lawton played in 11 games last season for the Colts at running back and on special teams. He had five rushes for 13 yards and four receptions for 29 yards, including a one-yard reception against Jacksonville on Dec. 2 for his lone career touchdown. Lawton also played four games for the New York Jets in 2005.
Bowie did not play at all this preseason due to a knee injury, the latest setback for the player acquired in the Randy Moss deal a year ago.
The Raiders selected Bowie with the fourth-round pick they got from New England for Moss last year. He played just two games as a rookie and now is out for his entire second season. Moss had 98 catches for 1,493 yards and an NFL-record 23 touchdowns for the Patriots last season.
Oakland did not sign a receiver to replace Carter, leaving Javon Walker and Ronald Curry as the only experienced wideouts on the roster for now. Rookie Arman Shields, who has been sidelined much of camp with a knee injury, did return to practice on Monday.
The entire backup group at wide receiver has just seven career catches. Johnnie Lee Higgins had six receptions as a rookie, and Chris McFoy has one career catch.
"We're looking at different things," Kiffin said. "I'm sure that our personnel department will find us a receiver, and add it to our group and see how far we can take him."