New signing Dzengis Cavusevic was sent off in Adelaide's 3-0 defeat to Melbourne Victory.
The Slovenian striker, playing just his second game for the Reds, was dismissed for slapping Victory's Rhys Williams shortly after his introduction as a substitute at AAMI Park.
The win. which was Victory's biggest at home in 11 months, puts them back above United into fourth place.
Two goals in a seven-minute spell in the first half put them on their way before Besart Berisha made the points safe with a third on the hour mark.
Three straight league defeats had put some pressure on coach Kevin Muscat, but he was happy with the way the team coped on their return from an Asian Champions League clash in China in midweek.
"If I can use a word to summarise it, I thought we were in control," said the coach. "I'm very pleased. We started very well and really caused them a hell of a lot of issues."
James Troisi, given the captain's armband in the absence of Carl Valeri, created the opening goal on 22 minutes when he headed Leroy George's cross towards goal. Keeper Paul Izzo and Taylor Regan couldn't deal with the ball and it went in off Regan for an own goal.
George then won and scored off a fabulous free kick after 29 minutes to extend Victory's lead.
United didn't manage a shot on goal in the first half, and when Cavusevic was dismissed 10 minutes after the break, it spelled the end for their chances.
Berisha made it 3-0 when he finished a free-flowing move on 59 minutes.
Adelaide coach Marco Kurz said his side's start hadn't been good enough.
"Today it was a very experienced team against a young team ... my boys in a lot of situations were too scared," he added.
Victory are 5/4 to win their next game against Melbourne City, who are 2/1 with the draw 13/5.
Victory are 9/1 to win the game 1-0.
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