"Both being super competitive, going for the ball," Cooper said. "We had a tangle-up at the ball, we both went to the ground. There was a lot of contact at the top of the route.
"It was nothing."
Williams was covering Cooper, broke up a pass from quarterback Michael Vick and both players went down. Cooper stood up and shoved Williams first. Williams responded with a couple punches and had to be forcibly restrained by teammates, including Vick.
Cooper walked away after cornerback Brandon Boykin stepped in to separate the players. Williams then took his helmet off, screamed at Cooper and started walking toward him before Vick stepped in and grabbed the fiery cornerback by his jersey. Williams yelled at Vick, and an assistant coach led the quarterback away.
"Our maturity level has to be on a whole different plane," Vick said. "Regardless of who the catalyst was for the whole fight, that doesn't matter. We have to be men. We're not guys who are out on the street, fighting one another. We're teammates. It's game week. We don't have time for that. I don't.
"It's a distraction."
The Eagles open their season against the Redskins in Washington on Monday night.
DeSean Jackson eventually calmed Williams, who is no stranger to fights. Williams found himself in a scuffle against an opponent when the Eagles and the New England Patriots held a joint scrimmage last month and was pulled from practice. He fought Jackson during a game last year when he played for Baltimore. He also shoved a referee during the Ravens' win over San Francisco in the Super Bowl.
"He's just one of those guys, he's a nagging person some times," Jackson said of Williams. "You get him on the field, he tries to be overaggressive, he tries to do things to intimidate receivers. Some people might back down from that. When you're dealing with people like myself, Riley, professional athletes, we all think we're as tough as each other.
"I think he's a good player, he's a competitive player."
Williams, signed as a free agent in the offseason, was a key part of Philadelphia's secondary overhaul. High-priced cornerbacks Nnamdi Asomugha and Dominique Rodgers-Cromartie were let go, replaced by Williams and Bradley Fletcher. The Eagles welcome Williams' physical play, though coach Chip Kelly warned him during training camp to avoid penalties and stay in games.
The Eagles immediately fined Cooper after the incident, which happened in June, and went public on July 31. A few days later, he left the team for sensitivity training. At that time, Williams said he had a problem not only with Cooper, but anyone who uses the word.
"Nobody should say it," Williams said. "I don't care if you white, black, blue, green or purple. The hip-hop culture uses the word and has de-emphasized it.
You need to go back and see what our ancestors did to try and rid themselves of that word."