Marrone's right leg twisted unnaturally in the turf after he landed awkwardly in just the fourth minute against his old team, forcing the accomplished defender and one-capped Socceroo to be stretchered off and rushed to hospital.
Gombau confirmed the worst in the post-match press conference, at the end of which he intended to visit Marrone in hospital.
"He'll be away from the game for three or four months," Gombau said.
"The doctor told me on the bench that he was going in the ambulance.
"He broke one bone (in the leg) but I don't know exactly which bone."
The injury to Marrone swiftly took the gloss away from Marcelo Carrusca's opening goal 26 seconds in - the fifth-fastest goal in A-League history.
"We lost it (our composure) for five or six minutes," Gombau admitted.
"Even me, the coach. I need to think what to do ... we put Fabio in right back.
"Sometimes when you go 120 per cent you don't think a lot.
"(For) the five or six minutes we were a little bit loose."
"We had four or five chances with 10 men," he said.
"I am so happy with how we played, the attitude and the players' run.
"From zero to 10, my team today is a 10.
"If we can play like this (for) 90 minutes, not just 45, I think we can beat everyone."
