Halloran's prognosis will be known soon after visiting a doctor but coach Marco Kurz has signalled the outcome.

"I think it's a long-term injury with Ben Halloran," Kurz told reporters on Thursday.

Halloran missed Adelaide's 4-3 win against Brisbane last weekend, when another attacker, Ken Ilso, copped a straight red card and subsequent suspension.

But the Reds have a ready-made replacement in new recruit Jordy Thomassen, who is likely to make his A-League debut in Saturday night's finals-shaping fixture against Melbourne City.

The fourth-placed Reds hold a two-point buffer over fifth-placed City and Kurz said Thomassen was in Adelaide's squad for the game.

"The boys, they do a great job to integrate him in the team," Kurz said.

"That is a big compliment to the group. It's not always easy to come in as a new player.

"Jordy is 100 per cent fit ... he looks like he's a good player. I don't know if he will start or not but he's ready."

Meanwhile, Kurz said he was surprised at Aurelio Vidmar's decision to quit the club after just five months as football director.

Vidmar, a former United coach and captain, cited unhappiness at being desk-bound by the role as the prime factor in his resignation.

"I was surprised that he left the club after only five months," Kurz said.

"We had always constructive, sometimes also controversial, discussions about a couple of things.

"But at the end it was always our goal ... to find the best solution for the club and that is what we did."

Kurz said he wouldn't get involved in discussions about whether Adelaide should appoint a new football director.

"I have enough work to do with my boys, to set the boys up and prepare well for the games," he said.