United's capture of the 26-year-old German was reported by some this week, but after Sunday's 2-2 derby draw with Brisbane Roar, Bleiberg revealed the deal was not yet complete.

"We haven't signed him," Bleiberg told FoxSports. "He still hasn't got his release from Nurnberg. We will know by tomorrow, so it's still not done.

"We are waiting for another marquee. Either we got two or we get none or one. Let's wait and see."

It is believed United's marquee target will be signed to replace influential skipper Jason Culina who is expected to be away on Socceroos duty during January at the AFC Asian Cup.

But Bleiberg said he'd give Brazilian midfielder Robson, who scored in Sunday's 2-2 draw, every chance.

"Jason (Culina) is going and we will miss him, but Robson is capable and he will take centre stage from now on," he said.

"I think we've got the depth and we can easily challenge for second place."