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.
But worse followed when fired-up Tarek Elrich was sent packing after picking up two penalty-conceding yellow cards in as many minutes, the disqualifying second coming after he apparently headbutted Aziz Behich in the 35th minute, which is sure to come under scrutiny during the week.
The Reds, racking up four yellow cards in five minutes at one stage, looked ragged and utterly undisciplined in falling behind 2-1 at half-time.
Gombau admitted his players lost composure, as did he himself when he strangely switched star winger Ferreira momentarily to right back, to replace Marrone.
"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."
But a spirited, impressive second-half revival was rewarded in the 92nd minute when Ferreira pinched a miracle equaliser after a plethora of Reds charges.
After such a chaotic, imploding first half, Gombau was ecstatic with the fightback and skill his side showed after the interval.
"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."
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