Everything went right for Western Sydney Wanderers in a combative derby win over Sydney as the champions had a six-match unbeaten run ended.
Western Sydney Wanderers have revived their stuttering semi-final hopes with a 3-2 victory in a spicy derby as Sydney were consigned to a first defeat in six matches.
Early goals from Bruce Kamau and Mitch Duke gave the out-of-form Wanderers a perfect start at Bankwest Stadium, before new recruit Scott McDonald completed the scoring on Saturday night.
The loss severely dents Sydney's hopes of defending their premiership with the Sky Blues trailing Melbourne City by four points, having played two matches more.
The Wanderers, for their part, are suddenly back in semi-final contention and are now level with sixth-placed Western United, albeit trailing on goal difference.
The Wanderers made the perfect start on 12 minutes as Kamau crashed home a rasping shot in off the near post with a first time finish from Ziggy Gordon's cross.
It was virtually the home side's first attacking foray yet unbelievably the Wanderers - winless since mid-March - doubled their lead inside four minutes.
This time Duke coolly slotted home after being teed up by Bernie Ibini's pivotal touch following Kamau's low cross.
The crowd, announced as 20,336, added a heightened atmosphere for the derby and the heat on the pitch was also elevated with three cautions in quick succession.
The match threatened to boil over on a couple of occasions with the contest resembling that of early derbies between the clubs.
Despite Sydney's exertions and vastly more first-half possession, there were few signs of the porous Wanderers' defence which had conceded 15 times in the past six matches.
However, the Wanderers, hopes of a steady start to the second half were soon swept away as the Sky Blues pulled a goal back barely 90 seconds after the restart.
And it was the least likely scorer imaginable with Sydney's defensive stalwart Alex Wilkinson heading home from a laxly defended corner for just his fourth goal in his 14th season of national league football in Australia.
The Sky Blues continued to dominate possession but clear goalscoring chances were relatively few despite constant promptings from the likes of Luke Brattan and Milos Ninkovic.
Wanderers' new signing McDonald entered with 25 minutes remaining for his club debut following his move from Brisbane Roar, and duly scored with virtually his first touch for his new club.
The veteran former Socceroo striker headed home directly from a corner nine minutes after entering the fray.
The Sky Blues' dominance in possession remained undiminished but a near-perfect night for the Wanderers was complete when Bobo blazed a hotly contested penalty over the crossbar in the dying minutes.
The Brazilian bundled home from close range four minutes into an elongated period of added time but the goal only underlined the heavy cost of the missed spot-kick a few minutes earlier.