Kewell could only watch on as his side slipped to a heavy defeat, with fans unhappy after seeing their side end the day in 21st place in League Two - just four points above bottom side Chesterfield.
The Sun reported that 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."
Crawley had held Wycombe in the first half, but Eberechi Eze's goal five minutes after the break and Craig Mackail-Smith's 11-minute hat-trick helped the home side romp to victory.
Kewell came under fire on Twitter from irate Crawley fans after the game.
According to the Crawley & Horley Observer 'a section of Reds' supporters vented their frustrations as the game wore on, with Kewell heading down the touchline after the final whistle to confront a small minority'.
Kewell told the newspaper afterwards:"We've all got to stick together and fight. Everyone understands that this is going to be tough, it's not going to be a stroll in the park.
"My players, myself, the staff and the fans all have to be together as one.
"I can understand that the supporters are upset at what they have seen. I'm not afraid, I'll stand up, I'm hurt by this as well. Like I said we are a team and teams must stick together."