"We are still waiting for the tour selectors to decide. If they ask for someone else to be sent instead of retaining Bilawal we will do the needful," Khan said in Lahore.
Speculations have been strong that the tour selection committee will send back all-rounder Bilawal who went for 93 runs against New Zealand in the second one-day international which Pakistan lost by a big margin in Napier.
Junaid, who was named in the World Cup's 15-member squad, was ruled out of the tournament on Monday after failing a fitness test in Lahore, but Khan said the selectors will decide the next line of action.
"Bilawal was not in the World Cup squad so we will have to get clearance from the technical committee to include him in the WC squad or some other player."
Pakistan's preparations for the World Cup have so far been awful as they have already lost champion spinner Saeed Ajmal due to an illegal bowling action while doubts also remain over whether Muhammad Hafeez would be able to bowl in the mega event after he was also suspended from bowling in international cricket by the ICC in November.