Sydney FC beat Macarthur Rams 3-1 in their first pre-season hit out at Campbelltown Stadium in western Sydney but the match was overshadowed by a brawl behind the goal reportedly involving between 20 and 40 people that resulted in one man being taken away in an ambulance.

Tensions rose when a group of men started antagonising the Sydney FC supporters while chanting Wanderers and RBB songs.

The clash then broke out as a flare was allegedly thrown at the Sydney FC fans.

One of those involved was seen throwing a bin and attacking security. A person was knocked unconscious by an apparent rival before the men dispersed when police arrived on the scene.

A small child was also reported to have been hit by a rock, although he was belived to have escaped without serious injury.

RBB spokesperson Sean Herrett said he was shattered to hear of the events because of the inevitable backlash on the group but insisted the perpetrators were not known to any of the RBB's regulars at the match.

“If it's people from the RBB, we're disgusted,” Herrett told au.fourfourtwo.com. “Initial investigations say it isn't.

"All the guys off the forum who were in the stands are saying it wasn't us. We don't know who they are.

“Obviously we don't condone that at all. We're about being inclusive and family-orientated. Last week we had kids with us in the RBB chanting.

“We've all been digging around for any piece of dirt because we want to know as well. If they're aligned with us at all, they will be punted straight out.

"We just want to show everyone what the best of active support is and it's not that type of crap. We're just shattered, I don't know how else to put it.”

Herrett said he had already spoken with a Wanderers representative to discuss a course of action in identifying the troublemakers and protecting the club and the RBB's images, starting with a meeting this week.

A mobile phone photo of the Wanderers group would be supplied to the club and police to help identify the culprits, he said.

Sydney FC CEO Tony Pignata has promised to ban any of his club's supporters who played a part in the trouble.

Pignata, who saw the events unfold, said he would come down hard on anyone found to be involved, regardless of who provoked who.

“I'm very disappointed with what happened tonight,” he told au.fourfourtwo.com. “A few silly fans ruin it for everyone and we need to stamp it out. It's 10 fans from each side that caused this stuff.

“I'll be speaking with (Wanderers CEO) Lyall Gorman tomorrow and the FFA, we really need to fix this and stop it from ever happening again. It's not what the A-League is about.

"We want families attending and there's a lot of people who saw that tonight who may never come to a game again. It's not good.”