But Waterhouse has confirmed veterinary tests on More Joyous revealed no serious injury and the trainer is confident her glamour three-year-old will be fit to continue her autumn campaign in the Group One Coolmore Classic next week.

Waterhouse revealed the More Joyous injury scare on the same day it was announced Blake Shinn had stepped down from his stable riding position. Shinn, 22, intends to now ride freelance but has reached an agreement with Waterhouse to still ride trackwork for Tulloch Lodge two days a week.

Sydney's former premier jockey has two rides for Waterhouse at Royal Randwick on Saturday - My Amelia in the Group Three $125,000 Sweet Embrace Stakes (1200m) and Princess Quality in the Listed $100,000 Wenona Girl Quality (1200m).

Waterhouse, who has secured Melbourne-based Brad Rawiller to ride promising Viking Legend in the Group One $350,000 Randwick Guineas (1600m) and Zutara in the Sweet Embrace Stakes on Saturday, admitted there were initial concerns about More Joyous' fitness soon after her Warwick Farm win last Saturday.

"She jarred up a little after that race," Waterhouse said.

"We had X-rays taken of her legs [Monday] to make sure nothing was wrong and fortunately they didn't show any problem.

"We gave the filly a cortisone injection and she is fine. I'm sure she will be fit and ready to go for the Coolmore Classic."

Waterhouse said More Joyous' effort to win the Surround Stakes last week was outstanding despite the filly having to fight hard to stave off Hurtle Myrtle and avoid a monumental upset. "I thought she ran a terrific race," Waterhouse said.

"With a filly like her, she has such brilliant, natural speed and the sit-sprint tactics probably didn't suit her."

Waterhouse said stable champ Theseo had emerged from his Chipping Norton Stakes triumph in "great order" and was on target for a fifth career Group One win in the Ranvet Stakes at Rosehill next week.

"He wasn't anywhere near fully fit for the Chipping Norton Stakes," she told The Daily Telegraph.

"We will decide after the Ranvet whether we continue to The BMW or perhaps switch back in distance."