Colchester United boss Joe Dunne has refused to defend the actions of Sanchez Watt after the forward was dismissed in Friday's 0-0 draw with Swindon Town.
Dunne's troops were forced to play out the remaining 23 minutes with 10 men after the former Arsenal youth team player was dismissed for aiming a headbutt at defender Nathan Thompson.
He told reporters: "He's apologised to everybody, the players and fans who have travelled. We don't want to see that on the football pitch, he was just frustrated.
"He'll learn from it and be better for it, but overall I can't defend him on that I'm afraid. The referee made the right decision."
The U's remain 14th in the League One table.