As bad as the scoreline looks, it still doesn't tell the full story of woe for the clueless Sky Blues who must pray for a speedy recovery by inspirational captain Alessandro Del Piero.
The Italian maestro strained his calf and trudged off Suncorp Stadium after 30 minutes never to return.
His exit, at 0-0 with his side doing their best to hang in, saw the floodgates open as the Roar ruthlessly punished sloppy defence with a three-goal blitz to effectively end the contest.
The Roar's energy and class was in stark contrast to the visitors and they should have racked up a bigger margin for the 21,841-strong Brisbane crowd but lacked finishing precision in a one-sided second half.
It was Sydney's eighth straight loss at Suncorp Stadium and showed Frank Farina has a massive task to turn them into worthy play-off contenders.
Even before the Roar started toying with them in the second half, the Sky Blues only once entered the home side's penalty area, compared to 26 at the other end of the field.
Socceroo McKay, playing his first game for the Roar since leading them to the 2010-11 title, shone in the onslaught after rushing back from this week's two international friendlies in Europe.
He was a constant menace in his 80 minutes in the midfield and superbly set up the third goal, pouncing on a Nicky Carle turnover to help Jade North break a five-year scoring drought just before half-time.
It was the third goal in seven minutes.
Skipper Matt Smith started the roll with a glancing header from a Thomas Broich free kick which keeper Vedran Janjetovic failed to stop.
A minute later, the Sky Blues' defence was embarrassed as McKay found Ivan Franjic from a corner who headed across to an equally-unmarked Henrique to finish from point blank.
By rights, the Brazilian could have finished with a handful wasted a litany of chances.
It took German playmaker Thomas Broich to supply the exclamation mark by finishing off a brilliant sideline run by stand-out winger Franjic in the 80th minute.
Despite the commanding performance, the Roar did finish with one worry as star striker Besart Berisha suffered a back injury in a clumsy first-half challenge by Marc Warren.
Earlier, two Marcos Flores penalties for Central Coast saved the Mariners' blushes on Saturday night, the defending premiers salvaging a 2-2 draw away to Melbourne Heart at AAMI Park.
A David Williams brace in the second stanza saw the Heart look set for the win, but two penalties in the space of four minutes allowed Graham Arnold's side to claim a point.
Heart's width and dynamic play provided a contrast to their anaemic opening round display against Melbourne Victory, as the home midfield looked to unleash Mate Dugandzic and Iain Ramsay at every opportunity.
The Mariners slowly edged into proceedings, however.
Trent Sainsbury's header onto the crossbar almost saw the Mariners hit the lead in the 23rd minute as the visitors started to dominate general play.
But it wasn't until half an hour later that the deadlock was broken, the Heart claiming the lead through David Williams off the back of a calamitous Justin Pasfield error in goal.
A hopeful long ball was knocked down to Golgol Mebrahtu, whose tame attempt from distance was spilled into Williams' path by the `keeper, the Heart attacker then coolly rounding Pasfield to hand his side the lead.
Six minutes later, Williams made it two after Nick Fitzgerald fluffed a golden chance at the other end.
Mebrahtu's incisive pass to Iain Ramsay forced the Mariners defence to scramble, and the Heart winger played square to an unmarked Williams for a simple tap-in.
The Mariners were given a lifeline in the 71st minute however, with referee Ben Williams awarding the visitors a dubious penalty, which Flores duly converted.
There were no doubts only four minutes later, as substitute Patrick Gerhardt was adjudged to have handled in the penalty area.
Flores went to his bottom left again, sending Andrew Redmayne the wrong way, but neither side was clinical enough in the final third to force a result.