Adelaide United defied the form line to shock Queensland Roar 2-0 at Hindmarsh Stadium on Sunday night to dash Frank Farina's team's hopes of ending up A-League premiers.

With their own finals hopes quashed a week ago, Adelaide gave retiring defender Richie Alagich a winning farewell in front of 10,803 fans with first half goals from budding Socceroos Bruce Djite and Lucas Pantelis.

The Roar's cause was further blighted just before halftime when tough midfielder Danny Tiatto was sent off by referee Strebre Delovski after the former Manchester City stalwart appeared to deck Adelaide United captain Travis Dodd off the ball.

The 34-year-old former Socceroo is now facing his third suspension of the season and could miss both legs of the elimination final against Sydney FC.

Most players then got caught up in a melee near the halfway line as Tiatto became engaged in a heated row with Adelaide players as he walked off.

Adelaide's first win since round 15 also ended a horror stretch of four consecutive losses which saw the side free fall out of the finals race.

Windy conditions made it tough going but United looked the most settled in weeks with Olyroo dynamo Nathan Burns back after injury and Jonas Salley shoring up midfield.

The Roar pressured in the opening minutes and won a series of corners with the breeze at their backs but only had a Sasha Ognenovski header powered wide in the 11th minute to show for it.

But Adelaide looked like a team on a mission in the first half and hard working Olyroo Djite got the break when the Roar keeper failed to hold a swirling cross from Cassio in the 18th minute.

Griffin McMaster spilt the cross under pressure from Dodd and Djite snapped his sixth goal of the season from seven metres out low into an empty goal.

Alagich had a goal disallowed for offside in the 27th minute but Tiatto's implosion off the ball in the 41st minute spelt disaster for the Roar as he was red carded after the referee consulted his assistant.

Adelaide made the Roar pay dearly in the 45th minute as Burns found Djite in midfield and he released Pantelis with a neat through ball and the Socceroo trainee made it 2-0.

United controlled much of the second half with their extra player but couldn't find the right finish to increase their lead.

Roar coach Frank Farina rued possibly his team's worst performance of the season against Adelaide but they must re-group quickly for the first leg elimination final against Sydney on Friday.

"I thought we didn't play that well tonight, specially in the first 18 minutes," he said.

"We conceded a dubious goal though the keeper Griffin McMaster was probably at fault to degree too.

"But once Danny (Tiatto) was off, it was over for us."

The Roar failed to fire a single shot on target during the match despite forcing 12 corners to none for Adelaide but managed to escape a bigger loss after half time.

"The delivery at set pieces was pretty poo. We didn't create chances tonight," Farina said.

He said "expected better" from Tiatto but hadn't seen the incident clearly.

"I will talk to him in the next couple of days but Danny has to be responsible. He's an experienced player," said Farina.

Key midfielder Matt McKay needs an MRI scan on an injured ankle and Craig Moore will probably use a hyperbaric chamber to help get over a niggling groin injury.

Adelaide coach Aurelio Vidmar said his team "didn't have a passenger."

"We kept our shape and got the goals at the right time," he said.

"They were committed tonight. It was great for the fans and for the future and a fitting end to a great A-League career (for Alagich)."

Dodd claimed Tiatto had hit him but denied Adelaide was trying to "bait" him.

"We didn't try to get him sent off," he said.

"Sometimes he just snaps and tonight he did."

Adelaide has a short break before fronting up for the first Asian Champions League match on March 12 in South Korea.

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