Sylvain Distin has warned Everton team-mate Marouane Fellaini that he must learn to cope with opponents who try to unsettle him.
Referee Mark Halsey and his assistants missed the incident, but the Football Association are expected to issue a violent conduct charge after reviewing television evidence.
Fellaini apologised for his headbutt via Everton's website on Saturday evening, and Distin believes the midfielder has to get better at keeping his cool.
"He is a good player for us and he's doing amazingly this season," the defender told the Liverpool Daily Post.
"He keeps scoring goals and if anything happens to him and he gets banned, I guess it'll be a lesson for him.
"We were talking about it before the game with him. In those kinds of games, they are going to try to frustrate him. He needs to make sure he doesn't react badly. It's a mistake and he will learn from it."