Sydney have come from behind to beat 10-man Perth 2-1 at ANZ Stadium on Sunday after Glory were denied a huge penalty shout in the dying stages.
The Sky Blues trailed 1-0 at half-time before goals to star duo Alessandro Del Piero and Brett Emerton turned the game on its head.
But the visitors will argue long and loud that they should have been awarded a penalty in the dying stages when Sydney defender Rhyan Grant handled in the box.
"It hit his hand. It's a definite penalty," Perth coach Ian Ferguson said.
"It was a guaranteed penalty and we didn't get it. I'm gobsmacked."
Sydney coach Ian Crook admitted it was a penalty.
Del Piero's goal came via the penalty spot after Steve Pantelidis brought down Emerton inside the box on 57 minutes.
Pantelidis was shown a red card and was halfway up the tunnel when Del Piero tucked away his spot-kick with a fortuitous ricochet off the left post.
Emerton sealed Perth's fate with a lovely chip over goalkeeper Danny Vukovic in the 70th minute.
The visitors kept coming and spurned at least three decent chances in the throes of full-time.
Perth have now gone nine matches across three years without a win against Sydney FC.
Things started well enough for Glory with Travis Dodd scoring after 18 minutes.
He collected the ball just inside the Sydney half after being set free by Steven McGarry and immediately made his way towards goal at pace.
He did Daniel Petkovski for speed before cutting back inside defender Trent McClenahan and beating keeper Ivan Necevski at the inside post with a sweetly-timed left-foot strike.
It was a lead Perth richly deserved after starting in an attacking frame of mind against the lacklustre and disjointed Sky Blues.
The hosts tried to work their way into the game but too often passes went astray, balls were over-hit or the wrong option taken.
Del Piero was a picture of frustration as his team-mates repeatedly failed to read his intentions or make the right runs.
Crook let fly with a few choice words at half-time - and it had the desired effect.
Sydney came out with a lot more intent and were rewarded with a goal 12 minutes after the re-start.
Ali Abbas played Emerton into the box with a lovely first-time ball but Pantelidis grabbed the Qantas Socceroo before he could pull the trigger.
It was a straight red card and an easy penalty decision.
Del Piero's penalty levelled things up and 12 minutes later Emerton put them ahead.
Vukovic ill-advisedly rolled the ball out to Liam Miller and he was harassed and dispossessed by Grant, who immediately passed to Emerton.
The Sydney captain deftly chipped Vukovic to give Sydney the lead.
Despite enjoying a one-man advantage, they were made to work hard right until the end as Perth kept pressing until the full-time whistle.
Sydney FC 2 (Del Piero 58, Emerton 70)
Perth Glory 1 (Dodd 18)