The Reds struggled to find their best form and after a 0-0 first half were put under pressure by the fleet-footed Steelers after the break.

However against the tide of play they found the match-winning goal; midfielder Diego chiming in to score at the 63rd minute.

A deft touch from Kristian Sarkies set up the Brazilian, who stormed forward and beat the right hand of Steelers goalkeeper Shin Hwa Yong with a crisp kick.

The downside to the 28-year-old's performance was his yellow card which sees him suspended for a game.

The result means the Reds remain at the top of Group E but they'll have to take a point away from their match against Changchun Yatai if they are to become the first Australian side to reach the quarter finals.

Both teams made a cautious start to the contest with the players knocking the ball around without any great conviction.

Adelaide showed promise early with Sarkies and Diego having shots on goal while Nathan Burns had some clever touches around the box.

But the visitors warmed to the task and started to win more of the ball.

Choi Jongbum put an accurate shot on goal after giving Richie Alagich slip and at the 36th minute Shin Hyungmin pulled the trigger from long range but the attempt sailed high and wide of the target.

Jonas Salley had a chance with a minute left in the half but his header (from a Sarkies' corner) kick lacked penetration.

The signs weren't good for the home side which wasn't getting enough from their attacking midfield players while their defence - which is without Ange Costanzo and Cassio - lacked drive.

Pohang came out firing in the second half with a long Song Changho strike testing Reds goalkeeper Eugene Galekovic for the first time.

And United's defence had some anxious moments as the Steelers earned two corners in a minute.

The Reds were under siege and down on confidence but Diego's goal changed momentum.

After conceding a goal, Pohang was rattled. Their keeper was under the greatest pressure with a handful of his clearances heading directly out of bounds.

But after a few player substitutions the visitors rallied, a Kim Jaesung centering kick cleared the Reds' defence but wasn't knocked home.

The Reds held firm in the final minutes, providing a fitting send off for Alagich, who played his last game at Hindmarsh Stadium.

Adelaide United 1 Diego 63'
Pohang Steelers 0 -
@ Hindmarsh Stadium. Crowd: 11,805