Sydney FC stun Postecoglou's Celtic

Ange Postecoglou's homecoming party has been crashed by Sydney FC, who came from behind to upset his Scottish powerhouse Celtic 2-1 at Allianz Stadium.

Prior to the Sydney Super Cup opener, local hero Postecoglou had not coached on Australian soil since resigning as Socceroos boss in late 2017.

The Australian has Celtic nine points clear at the top of the Scottish Premiership table, and with only four players missing on World Cup duty the Bhoys appeared destined to roll through a Sydney outfit that has started 2022-23 unconvincingly.

But the Sky Blues silenced the pro-Celtic crowd with a tenacious performance, back-up goalkeeper Tom Heward-Belle shining and inexperienced defenders Aaron Gurd and Adrian Vlastelica announcing themselves.

Frustrated in defeat even without competition points on offer, Postecoglou refused to blame the long flight over for his team's loss.

"I'm not a violin player, mate. We get on with it," he said.

"(The players) probably are tired, but so what? The game was today, not tomorrow.

"We were nowhere near it today.

"We set expectations and levels, and if we fall below that then it's disappointing, irrespective of the circumstances or what the environment or the competition is."

As has been the case so far this A-League season, wingers Robert Mak and Joe Lolley were Sydney's most dangerous players in the front third early on - both rattling the crossbar by the mid-point of the first half.

The home side could consider themselves unlucky to have conceded first when Liel Abada's strike ricocheted into the net off Kyogo Furuhashi in the 23rd minute.

The Sky Blue faithful appealed for offside but with VAR on holidays for the Sydney Super Cup, the goal stood.

Undeterred, Mak had Sydney back on level terms less than three minutes later, winning a footrace against Celtic's Stephen Welsh and earning himself a one-on-one with 'keeper Benjamin Siegrist at point-blank range.

At the other end, Heward-Belle's finest moment came just before the break, when his leg blocked Furuhashi's strike to keep the scores level at halftime.

"He pulled off some good saves," Postecoglou said. "They defended well in the box when they needed to."

Postecoglou brought on a handful of his regular starters after the interval and the fresh legs helped Celtic take control.

But Max Burgess' left-footed strike from just inside the box had Sydney up 2-1 against the run of play and dreaming of an upset in the 60th minute.

Sky Blues coach Steve Corica cycled through the bench as Sydney held on for a famous win despite losing the battles for shots on target (8-5) and possession (64.1 per cent to 35.9 per cent).

"It was really good for the boys' confidence, to win against a quality side," Corica said. "We're very pleased with that."

For their second and final game of the Sydney Super Cup, Celtic face English Premier League side Everton at Accor Stadium on Sunday.