Nathan Berry's brother Tommy and his father-in-law Glyn Schofield have flown to Singapore where the jockey is in hospital suffering from viral encephalitis.
Tommy Berry and Schofield will not ride at the Group One meeting at Rosehill on Saturday.
Nathan Berry became ill on Tuesday at trackwork at Kranji Racecourse and has been in hospital since his collapse.
He was due to fly back to Sydney this weekend to ride Golden Slipper contender Unencumbered in the Todman Stakes.