Trailing by two goals with just five minutes to go, United's cause was given hope when Reuben Way headed home to reduce the deficit, then with Sydney's defence visibly rocking, Tahj Minniecon levelled with a neat finish just a minute later.

But the drama didn't end there. In the final seconds Golgol Mebrahtu capitalised on Sydney's inability to clear their lines and gleefully smashed home the winner to complete an amazing recovery by Mike Mulvey's youngsters.

Gold Coast adapted well to the wet, blustery conditions, dominating the early phase of the match, but it was Sydney who fashioned the best openings with the lively Kerem Bulut forcing Jerrad Tyson into a save and Joel Chianese also going close.

Tyson was called into action once again midway through the half, this time saving acrobatically from Iain Ramsay's goal-bound header. The flurry of chances for the visitors jolted United into action and they hit the front on 22 minutes with a fine goal from striker Chris Harold.

Tahj Minniecon was the creator, intercepting on the edge of the box then feeding Harold who steadied himself before blasting a bullet of a shot past Vekic in the Sydney goal.

But just two minutes later it was all square again when Dimitrios Petratos levelled for the visitors with a superb 25-metre free-kick that left Tyson helpless.

The arm wrestle continued after the break with both sides going all out for the win. For United, Andrew Barisic and Callum Hare both went close with headers, then Bulut gave Tyson more work to do with a close-range effort.

Bulut found the net soon after though when he connected with Ramsey's cross to divert the ball past Tyson and give the visitors a surprise lead on the hour mark.

Coach Mike Mulvey introduced Mebrahtu and Way into the action as Gold Coast threw everything at Sydney in search of the equaliser.

But they were dealt a sucker punch as with just over a quarter of an hour to go. Petratos swung in a corner from the right-hand side and substitute Joseph Gibbs rose highest to nod home despite Mitch Bevan's attempted clearance. 

Cue United's fightback. First, the unmarked Reuben Way headed home Bevan's corner five minutes from time, then Tahj Minniecon showed his quality with a classy finish after his run was picked out by a fine Richard Greer pass to level the scores at 3-3.

In the final seconds, United completed their comeback when Mebrahtu thumped home the winner to secure a vital win for the home side in the most dramatic fashion.