Attorney Harvey A. Steinberg entered Cox's plea Monday during a hearing in Castle Rock, in suburban Douglas County south of Denver, and District Court Judge Paul King set a trial date of Oct. 18, six weeks into the NFL season if the labor dispute and lockout is resolved.
Prosecutor Robert Chappell and Steinberg estimate Cox's trial would last six days.
Cox is charged with one count of sexual assault while the victim was physically helpless and one count of sexual assault while the victim was incapable of determining the nature of the conduct. Court documents say the alleged assault happened on Sept. 6. He was arrested Dec. 9 and is free on $50,000 bail.
Cox did not speak in court. After the hearing, two Broncos fans recognized him walking through the hallway, smiled, called his name and shook his hand.
"It's tough. It's something that stays over your head," he said as he walked out of the courthouse. "You stay positive and just control what you can control."
Cox, a Waco, Texas, native, said he's back in Colorado, where he's working out every other day in hopes that the NFL and players association can reach an agreement and end the lockout and start the season as scheduled on Sept. 8.
Details of the charges remain under seal at the request of prosecutors and Cox's defense attorney. The seal is being contested by The Associated Press and The Denver Post. King set a June 2 hearing for arguments on that matter, which Cox does not need to attend.
Cox is due in court again Aug. 26 for a motions hearing.
Cox, a fifth-round draft pick out of Oklahoma State, started nine games for the Broncos his rookie season playing opposite cornerback Champ Bailey.
Cox was among a string of Broncos players who got into legal trouble last season. Linebacker D.J. Williams was stripped of his captaincy after his second drunken driving arrest and rookie linebacker Kevin Alexander was waived hours after his arrest on a domestic violence call in December. Prosecutors later dropped domestic violence charges against Alexander after the woman he was accused of hitting refused to cooperate.
Prosecutors dropped assault and disturbing the peace charges filed against Broncos defensive end Elvis Dumervil over an altercation with a parking lot attendant before a game on Oct. 24.
Shortly after the season ended, running back Laurence Maroney, whose contract is up, was arrested on guns and drug charges in St. Louis.
In a January letter to season-ticket holders, team owner Pat Bowlen pledged to restore integrity and a winning culture to the team. Bowlen hired Hall of Famer John Elway as the team's chief football executive and Elway in turn hired John Fox as coach.