Kewell went over to talk to allegedly "abusive" supporters following the defeat.
But the scene soon turned ugly with the former Leeds and Liverpool forward reportedly having to be pulled away by his players after security intervened.
Speaking afterwards, Kewell said: "Look, I'm not a shy person. I'll confront anybody.
"I said at the start that if you have a problem you can always come up and ask me but, you know what, just leave it, because you're never going to win."
One person who claimed to be in the crowd alleged that Kewell "came over with a red face" shouting "F off", reports The Sun.
Crawley manager Harry Kewell held back by players and security during angry confrontation with fans https://t.co/o46Qml6nmv— Steve Johnson (@saj1964) November 18, 2017