Benitez was allowed to fly home on Monday by Blues after his father suffered head and neck injuries in a road accident.
City boss Alex McLeish spoke to one of his advisors on Wednesday night and was told Benitez senior is "not in danger" in terms of the injuries being life threatening.
But the logistics of making the lengthy trip back from Ecuador, and having insufficient time to recover physically, means Benitez junior is unlikely to return for the weekend.
McLeish said: "I spoke to the guy who helped Christian through his deal when he came here. He said Christian went to see his father in hospital last night.
"He expected to hear from him last night but never had any communication.
"So it looks as if it is going to be difficult to get him back for this weekend given the fact he would then be leaving us again on Sunday to go back to Ecuador for World Cup games.
"We understand his father is not in danger and that's the biggest concern. He got shunted from behind in the accident, got a head wound and a neck injury and we wish him a speedy recovery."
McLeish added: "Christian wanted to come back if he felt his dad was okay but he maybe feels he has to be with him at the moment.
"We should hear more later today but, given this is Thursday, it will be very difficult. We have plenty of options.
"We would have liked him to be one of the options but, if it is not to be, we have to deal with it and we have good players who can slot in there."
Defenders Stuart Parnaby and Franck Queudrue could be back from injury for the trip to Turf Moor.