The former Premier League attacking midfielder who captained his country, Slovenia, at the 2010 World Cup, would have been the ideal replacement for the departing guest player David Villa, who goes back to New York for what City officials hope will only be a short break after the round four clash with Adelaide on October 31.

But coach John Van 't Schip on Wednesday morning said Koren's prognosis was worse than hoped and he would not be available for several more weeks.

"He got a setback on Friday when we were training at AAMI Park, and we got the results back the day before yesterday from an MRI and it's not looking better. He's going to be out for a few weeks and that's a big disappointment.

"It's hard to know when he will be back. It's going to take a few weeks. Five or six weeks. Its a disappointment for all and for Robi its the biggest disappointment.

"His injury seemed to be very little, but he reinjured himself in the same spot and its going to take longer. We can't take any risks. We wanted to have him coming out of the midfield and into scoring positions. He showed in pre-season that he has scoring and passing abilities, but it's a big miss."

Van 't Schip said it was unlikely the club would seek to sign any foreigner on a short term deal. "Where do you get someone in for five weeks. It has to be someone who is not playing and is probably out of condition."

The Dutchman said that talks over Villa's future would take place this week.

"I am confident with David that he is happy here. There will be some talks in the coming days but I am confident he will continue. We know the situation but we should not make it bigger than it is. He made two very important goals but it doesn't take away from the team, we are playing good football. He has showed his class."