Sydney FC have won their fifth consecutive derby with a come-from-behind 3-1 victory at ANZ Stadium on Saturday night - aided by a horrible error from Western Sydney Wanderers goalkeeper Vedran Janjetovic.
With Wanderers up 1-0 following Oriol Riera's first goal in three matches, Janjetovic inexplicably charged out of his penalty area and eventually handballed Adam Le Fondre's shot, with referee Jarred Gillett having no choice but to produce a red card.
The Sky Blues slowly wore down their weakened opponents, with Alex Brosque striking on the stroke of half time before marquee Siem De Jong made it two in the second half.
Substitute Jacob Tratt sealed the match late on with a thumping header on his debut for the club.
A vicious electrical storm saw kickoff delayed by 30 minutes and once the players emerged from the sheds, it was the Wanderers who were the much better team in the early stages.
Markus Babbel's men got their just reward on 23 minutes when Riera managed to side-foot Alexander Baumjohann's cross into the net after hesitation from Sky Blue goalkeeper Andrew Redmayne.
But barely three minutes later the match was flipped on its head when Janjetovic charged out of his area to confront a contest between Le Fondre and Josh Risdon.
The Wanderers goalkeeper failed to impact the duel and after Le Fondre nicked the ball, Janjetovic inexplicably used his hands to save the Englishman's shot toward a vacant net that was getting covered by red and black defenders.
Babbel was forced to withdraw playmaker Baumjohann to bring on replacement goalkeeper Daniel Nizic and the Sky Blue dominance of the match began.
After 20 minutes of sustained pressure, Brosque made the breakthrough just before the break, prodding the ball into an empty net after Josh Brillante's low drive rebounded off the post.
It was inevitable the Sky Blues would take the lead and it came on 57 minutes, when De Jong smashed the ball home following the Wanderers' poor efforts to clear a corner.
Tratt, who replaced the cramping Aaron Calver, put the icing on the cake, heading home at the back post to send the Sky Blue fans wild.
The only downer on the right for Sydney FC was a suspected knee injury to Dutch defender Jop van der Linden - with Brandon O'Neill filling in at centre half.
Sydney FC remain in third position, three points behind Perth Glory, who play on Sunday against Newcastle Jets, while the Wanderers stay in eighth with only two wins from their eight games.