Robson had reportedly been considering a move for the Australian, but Milligan's agent Richard Briggs has insisted the 22-year-old will be staying down under for the foreseeable future.
Briggs said: "He won't be going anywhere at this stage. For a start, he does not have a British passport and that's the problem for a lot of the lads in the A-League.
"There is of course the opportunity to get around things by getting a club in Europe, the route other Australians have taken.
"But that does not appeal. Our main focus is to keep him settled for at least the next three to four months. He has a contract with Sydney FC and that's where things stand."