Asomugha didn't reach certain incentives this season, voiding the last year of a three-year, $45.3 million contract and making the three-time Pro Bowl cornerback an unrestricted free agent, a source with knowledge of the deal said Sunday.
Raiders senior executive John Herrera later confirmed to The Associated Press that the contract had been voided. The 2011 option was worth either $16.8 million or the amount of the quarterback franchise tag, whichever is greater.
The Raiders now must decide whether to pay big money to keep Asomugha or use it to shore up other positions.
"We have to wait on the ramifications of the new CBA to be able to move on," Herrera told The AP.
The Raiders could have many other key free agents this offseason, depending on the terms of the new collective bargaining agreement. Pro Bowl defensive tackle Richard Seymour, safety Michael Huff, cornerback Stanford Routt, tight end Zach Miller, left guard Robert Gallery and running back Michael Bush are among the Raiders' other potential free agents.
Entering this season, Asomugha had to participate in more plays or boost his interception, fumble recovery or sack totals from their 2009 levels to pick up the last year of the contract. But Asomugha played in just 14 games -- two less than 2009 -- because of an ankle injury, and he didn't post an interception, a fumble recovery or a sack. He also had 19 tackles, 15 fewer than last season.
The Raiders can't use their franchise tag on Asomugha, who will be 30 next season, because of another clause in the contract, which the cornerback signed in February of 2009. Asomugha was paid $28.5 million in the first two years of the deal.
Asomugha, a first-round pick (31st overall) by the Raiders in the 2003 NFL Draft, struggled while moving from college safety to NFL cornerback, then had a breakout season in 2006, posting eight interceptions, including one returned for a touchdown. He has just three interceptions since then, but that can be attributed to opposing teams choosing to throw away from him.
According to STATS LLC, Asomugha was targeted on just 33 pass attempts this season. He allowed 13 completions for 205 yards and no touchdowns, burnishing his reputation as a shutdown cornerback.
The Raiders haven't been able to put a winning team on the field during Asomugha's eight years in Oakland. The team lost at least 11 games for an NFL-worst seven consecutive years in Asomugha's first eight seasons before improving to 8-8 this year.
That improvement didn't satisfy Raiders owner Al Davis, who announced last week that he wouldn't pick up the option on coach Tom Cable's contract. The Raiders are now searching for their sixth coach since 2003, with offensive coordinator Hue Jackson the leading contender.
The Associated Press contributed to this report.