In-form Sydney jockey Jason Collett will replace the suspended Corey Brown on Ef Troop in the $3.5 million Golden Slipper on Saturday week.

Brown was unsuccessful on Friday in an appeal against a suspension from last Saturday's Randwick meeting but not enough to ride on Slipper day.

Brown rode Ef Troop when he finished second to Aylmerton in the Todman Stakes last Saturday and was offered the Slipper ride.

After Brown was suspended, Brisbane trainer Tony Gollan rang Collett who agreed to stand by for the ride.

"It is bad luck for Corey as he had committed to my horses for the Slipper. But Jason is riding very well and he is very experienced," Gollan said.

"The Slipper is a race for big name jockeys and Jason is right up there with them. I am really looking forward to the Slipper as I think Ef Troop will be clearly improved."

Gollan said he was resigned to stablemate Outback Barbie missing the Golden Slipper on Saturday week.

"It is also bad luck because she has been improved by her fifth in the Reisling Stakes but she isn't going to make it unless there are mass scratchings," he said.

"But she will stay in Sydney for the Percy Sykes Stakes next month."