McCoy was briefly knocked out of the game in the fourth quarter when he was the victim of a helmet-to-helmet hit by Pittsburgh's James Harrison, who was penalized for unnecessary roughness.
Seneca Wallace replaced McCoy at quarterback, but McCoy was soon back in the game and led the Browns to the Pittsburgh 6-yard line with his team trailing by seven points. McCoy then threw an interception in the end zone.
After the game McCoy's father told The (Cleveland) Plain Dealer his son should never have come back on the field.
"He was basically (knocked) out," Brad McCoy told the newspaper. "You could tell by the rigidity of his body as he was laying there. There were a lot of easy symptoms that should have told them he had a concussion.
"He was nauseated and he didn't know who he was. From what I could see, they didn't test him for a concussion on the sidelines."
Browns Coach Pat Shurmur said he was not aware until after the game the quarterback had concussion symptoms.
"I was told that Colt could go back in the game," Shurmur said. "He came up right next to me and said 'I'm ready to roll,' so he went back in."