Tony Taylor, 34, who will be sentenced Dec. 14, said he was not promised any specific sentence in return for his cooperation.
Taylor faces a maximum of five years in prison and a $250,000 fine, but federal sentencing guidelines likely will call for less. The guideline range will be determined by the court's probation office, and U.S. District Judge Henry E. Hudson can depart from that range if he finds aggravating or mitigating circumstances.
"You're pleading guilty and taking your chances, right?" Hudson asked Taylor.
He responded, "Yes."
Taylor had the same answer when Hudson asked: "You have agreed to cooperate fully with the United States, is that right?"
Taylor, of Hampton, entered his plea to conspiracy to travel in interstate commerce in aid of unlawful activities, and conspiring to sponsor a dog in an animal fighting venture.
Vick and two other co-defendants pleaded not guilty last week to the same charges.
The written plea agreement requires Taylor to "testify truthfully and completely at any grand juries, trials or other proceedings." It says any truthful information provided by Taylor cannot form the basis of a stiffer sentence or additional charges.
Prosecutors already have said a superseding indictment will be issued next month, which could mean more charges against Vick and the remaining co-defendants.
Taylor and his attorney, Stephen A. Hudgins of Newport News, refused to answer reporters' questions as they left the federal courthouse after the 15-minute hearing.
Prosecutors claimed in a July 17 indictment that Taylor found the Surry County property that Vick purchased and used as the site of "Bad Newz Kennels," a dogfighting enterprise.
"The `Bad Newz Kennels' operation and gambling moneys were almost exclusively funded by Vick," a statement of facts supporting the plea agreement and signed by Taylor says.
The statement also lists several dogfights that Taylor claims Vick attended in Virginia and other states. The principals in the dogfighting ring split any winnings, and Taylor - who spent most of his time raising and training the pit bulls - used his share for living expenses, according to the statement.
Taylor also confirmed the indictment's claim that he helped purchase pit bulls and killed at least two dogs that fared poorly in test fights.
According to the 18-page indictment, the dogfighting ring executed underperforming dogs by drowning, hanging and other brutal means. It alleges that the fights offered purses as high as $26,000.
Taylor left the enterprise after a falling out with co-defendant Quanis L. Phillips and others in September 2004, according to the statement of facts.
The grisly details outlined in the indictment have fueled protests and public outrage against Vick. NFL commissioner Roger Goodell has banned Vick from the Falcons' training camp while the league investigates.
Vick and Purnell A. Peace, 35, of Virginia Beach, and Phillips, 28, of Atlanta, are scheduled for trial Nov. 26. They remain free without bond.