Doctors have ruled Winona Costin unfit to ride at Rosehill after the leading Sydney apprentice failed a concussion test.

Costin was one of four jockeys involved in a serious fall at Canberra on Sunday.

She was taken to hospital and after her release later that night Costin had hoped to gain a medical clearance to allow her to ride at Rosehill on Wednesday.

But a Racing NSW doctor's assessment after trackwork on Tuesday morning soon put paid to her plans to take four midweek rides.

Costin will also miss Thursday's NSW provincial meeting, but she is expected to be cleared to return to the saddle for the Group One Chipping Norton Stakes meeting on Saturday.

"The doctor has advised she should be free to resume riding at Randwick should she pass an after-injury cognitive test on Thursday," Racing NSW steward Marc Van Gestel said.

Replacements have been made for three of her four Rosehill rides.

Andrew Adkins goes onto Self Esteem, Brodie Loy takes over on Junoesque and Koby Jennings rides Godolphin galloper Nazca.

Costin was crowned champion Sydney apprentice last season despite parting ways with Gai Waterhouse towards the end of 2014-2015 to link with Peter and Paul Snowden.

She is well placed to go back to back being only three wins behind Rory Hutchings, the former New Zealand apprentice indentured to Chris Waller.

Hutchings has a limited Rosehill book, but his chances of increasing his lead are bright as he takes the ride on the Waller-trained Hursley.

Entered for the Australian Guineas, Doncaster Mile and ATC Australian Derby, Hursley warmed up late in the race for a midfield finish at Warwick Farm at his first run since winning at stakes level during the Melbourne Cup carnival.

Hursley heads betting in first corporate bookmakers' markets on the Peter Malone Handicap with Hutchings' 1.5kg claiming reducing the colt's impost to 60kg.

Unbeaten Godolphin filly Asinara will run as the shortest-priced favourite for the meeting, going up odds-on in the Di Parker Handicap after wins at Kembla Grange and Rosehill.