A late header from Western Sydney captain Mitch Duke brought a dramatic end to Sydney FC's 13-game undefeated A-League streak on Friday night.
A cross from Tate Russell nine minutes from time found the head of Duke who nodded home to give the 10-man Wanderers an unlikely 1-0 victory.
In a thumping atmosphere at the sold out Netstrata Jubilee Stadium, the visitors handed the Sky Blues their first loss since round three.
The competition leaders must have thought they were seeing double - that previous reverse was also a 1-0 defeat to their bitter cross-city rivals.
A raucous crowd of more than 18,500 was kept on the edge of their seats throughout as both sides created chances but were denied by good defence.
The Sky Blues were kept in check by the Wanderers all across the park and signs of frustration started to show as time ran down.
Effective tactics from Wanderers' caretaker coach Jean-Paul de Marigny kept the ladder leaders searching for space they were not afforded.
"It's a process we've been working for," de Marigny said.
"Things that happened tonight was hard work by the players and staff to get the environment right we get the players to enjoy their football.
"It's pleasing to see that we're more than competitive. I felt really comfortable. I knew there was moments we were going to create, it was just about being ready for them and believing in them."
The win is the second in a row for Western Sydney, who are now undefeated from four games under De Marigny since he took over from sacked coach Markus Babbel.
Wanderers fans at the southern end of the stadium intensified the atmosphere on the night by setting off at least five flares throughout the match, while the antics continued outside the ground, leaving the club open to sanctions from the FFA.
The fiery feelings were also apparent on the field, with Daniel Georgievski copping a late red card for lashing out with a boot at Marco Tillio's face after an untidy challenge.
Fuming Sydney FC coach Steve Corica confronted Georgevski in the tunnel after the match, with the moment caught on camera by broadcasters Fox Sports.
"I thought he obviously deserved the red card for kicking out at Marco Tillio, so that's the way it goes. That's football," Corcia told media in the press conference.
"He's a competitor and he made a mistake as well, kicking out, because you can't have that. Especially in the face."
In-form Wanderers midfielder Bruce Kamau was taken off in the 55th minute with what looked like an adductor injury, although it is not believed to be serious.
Sydney FC will travel to play Melbourne Victory at Marvel Stadium on March 7, while the Wanderers face Brisbane Roar at Suncorp Stadium on March 6.
Australian Associated Press