The £32.5 million signing from Real Madrid was expected to make his comeback against Southampton in the Carling Cup next week but a stress-fracture to his ankle has failed to heal adequately.
"Robi is not ready to come back into the group yet, but he is not far off. It is unlikely he will be fit to play against Scunthorpe," City manager Mark Hughes said.
"The best we can hope for is that if he gets back into training he could possibly be on the bench, but even then it's a little bit too soon."
There was better news concerning injuries to Craig Bellamy and Kolo Toure ahead of their Premier League contest with Fulham on Sunday.
"Kolo was due to do some light training today, so we are hopeful he will be OK for Sunday, Craig will probably be back in training in Friday," Hughes said.
"He has been working with the physio and has done OK so we will try to reintroduce him to the group towards the weekend with a view to him being available for selection."