The NFL Players Association asked a federal judge to overturn a special master's decision that Vick should forfeit the bonus money because of his guilty plea. The former Atlanta Falcons star faces up to five years in prison when he is sentenced Dec. 10.

Dogfighting wasn't the issue at Friday's hearing. Instead, the arguments turned on interpretations of the NFL collective bargaining agreement.

Union attorney Jeffrey Kessler argued that Vick's "roster bonus" should be treated the same as a "performance bonus," which can't be forfeited under the collective bargaining agreement.

"A roster bonus is a performance bonus," Kessler said, explaining that Vick earned it simply by being on the Falcons' roster in 2005 and 2006, and that the money a player earns can't be taken back under the contract.

But Gregg Levy, representing the NFL, said the roster bonus should be treated like a "signing bonus allocation," which could be forfeited.

The term "signing bonus allocation" isn't explicitly defined in the contract and only appears in it a few times. Pointing to some language under the salary cap section, Levy argued that it's similar to a signing bonus, which can be stripped from a player under certain circumstances. He said that because Vick's roster bonus had been guaranteed, it shouldn't be treated as if it was money Vick had earned for meeting performance standards.

District Judge David Doty, who has handled cases involving the collective bargaining agreement for nearly 20 years, compared interpreting the relevant section of the contract to "alchemy." He didn't say how or when he might rule.

Outside the courtroom, players union chief Gene Upshaw said the union wasn't defending Vick's actions by pursuing the case.

"This is not about Michael Vick. This is not about dogfighting. This is about interpretation of the contract and what it means," he said.

Special master Stephen B. Burbank ruled last month that the Falcons were entitled to recover $19.97 million in bonuses paid from 2004 through this year. The Falcons argued that Vick used proceeds from a $130 million contract he signed in 2004 to finance his illicit activities.

Any money recovered would be credited to Atlanta's future salary cap.

Separately, two of Vick's co-defendants were sentenced Friday in Virginia to 18 months and 21 months in prison on federal dogfighting conspiracy charges. Quanis Phillips and Purnell Peace each had faced the same maximum penalty that Vick faces.