A hat-trick from former Sydney FC attacker Dimitri Petratos has helped Brisbane Roar to a crushing 5-2 win over the Sky Blues on Boxing Day.
Despite going behind to a brilliant early Alessandro Del Piero free-kick, the Roar had too much class and firepower and set up the easy win with three goals before the break in front of almost 18,000 fans at a wet Allianz Stadium.
Thomas Broich, playing in a central striking role in place of the injured Besart Berisha, got the equaliser before Petratos came back to haunt his former club.
The 21-year-old, who had a messy split with the Sky Blues last year before leaving for Malaysia, converted a penalty in each half and also finished off a sublime team move to complete his first senior treble before Ivan Franjic and Sydney's Richard Garcia both scored in stoppage time.
The victory sees the Roar become the first side in the competition to notch 100 A-League wins and ensures Mike Mulvey's side head into 2014 on top of the ladder.
Sydney have now lost three of their last four games and their horror night was compounded when Del Piero was forced off at half-time through injury.
With an average of over 30 it was the oldest team Sydney have ever fielded and it showed as they looked tired and too slow against the rampant league-leaders.
After withstanding an early onslaught from the visitors, Sydney opened the scoring against the run of play on 11 minutes via another piece of magic by Del Piero.
The Italian was fouled just outside the box but picked himself up and planted a dipping free-kick over the wall and past Michael Theo, who got two outstretched hands on the ball but couldn't keep it out.
It was Del Piero's fifth goal of an injury-disrupted season and fifth in just five appearances against the Roar.
But in the blink of an eye their advantage evaporated as the Roar struck twice in three minutes through Broich and Petratos.
Luke Brattan's defence-splitting pass sent Broich clear through on goal, with the German steadying himself before finishing clearly past Vedran Janjetovic.
And before the Sky Blues could regroup from that setback they fell behind.
Henrique was causing huge problems down Sydney's right and it was no surprise he was involved in the goal, brought down inside the box by a clumsy tackle by Sebastian Ryall.
Petratos blasted home from the spot and despite being forced to retake his effort made no mistake again to give the visitors a deserved lead.
It got even better for the Roar 10 minutes before the break when Petratos had his second with the goal of the night.
Matt McKay and Broich combined brilliantly on the edge of the box, toying with the static Sydney defence before the latter teed up Petratos who finished powerfully into the roof of the net.
Without the class and guile of Del Piero Sydney never seriously threatened a fightback in the second half, despite a vastly improved showing.
But the Roar still manufactured a host of chances with McKay and Henrique both going close before Petratos completed a dream return to Sydney with his hat-trick 12 from time.
Franjic added icing on the cake with a goal at the death but there was still time for Garcia to add a consolation goal in the final minute of stoppage time.
Sydney FC 2 (Del Piero 11, Garcia 90+4)
Brisbane Roar 5 (Broich 20, Petratos 23, 35, 78, Franjic 90+3)
Crowd: 17,662 @ Allianz Stadium