Brisbane defender Avraam Papadopoulos spat at Sydney FC striker Matt Simon in an ugly incident, marring the Sky Blues' 3-1 A-League win.
Sydney were up 2-0 with 18 minutes to play on Saturday night when the pair clashed at Allianz Stadium.
Replays showed Papadopoulos clearly spitting in the direction of Simon, who retaliated by grabbing the Roar player's shirt near his neck before he went to ground.
A video assistant referee (VAR) review was called and referee Alex King took more than a minute to analyse the footage before issuing both players with straight red cards.
The episode put a dampener on an otherwise high-tempo game that sent Sydney back to top spot and exposed the Roar, who were attempting their second win of a trying season after last week's breakthrough against Melbourne City.
After another short turnaround following Tuesday night's FFA Cup final win, Graham Arnold trusted a second-string side to deal with their eighth-placed counterparts, leaving Bobo on the bench and Milos Ninkovic and Michael Zullo out of the squad.
It didn't matter -- by the 13th minute, the hosts had rushed to a two-goal lead.
Adrian Mierzejewski was the creator of David Carney's seventh-minute opener via a through ball to Simon, the stand-in frontman executing an expert quick flick-on for Carney to slide home.
The Roar barely had time to regather when Jacob Pepper was pinged for handball after Luke Wilkshire's cross rebounded off Carney and took a deflection off the defender's outstretched arm.
The VAR came knocking but the decision stood, controversially so according to viewers on social media, who also took issue with Alex Brosque's missed handball in the lead-up to Carney's goal.
From that point, the Roar, not short of intent but wanting in their finishing, lost their zeal as Josh Brillante ran riot and Brandon O'Neill accounted well for Massimo Maccarone.
They awoke after the break to fashion a glimmer of hope, and Andrew Redmayne could be thankful for the offside flag.
Maccarone's header off a free kick left the goalkeeper on his bottom, as the ball scuffed off his studs and into the path of Pepper to finish.
The contest exploded into anger and farce as the 10,044 in attendance jeered Papadopoulos' spit and reacted with disbelief when Simon reacted to the insulting gesture.
Jordy Buijs picked out Seb Ryall on a free-kick and the defedner put a bullet header past Young for Sydney's third.
But Brisbane managed to claw one back when the tireless Brett Holman set up Jack Hingert and his deflected striker nestled into the net.