Charlie Boy will run in Sunday's Caulfield Guineas Prelude rather than the Sir Rupert Clarke Stakes, delaying Jim Cassidy's quest for a 100th Group One win.

The champion jockey will now have to wait until Epsom Handicap day in Sydney on Saturday week to become just the third rider to reach the milestone.

Trainer Gerald Ryan said the Prelude (1400m) against his own age group was the preferred lead-up for the three-year-old going to the Group One Caulfield Guineas (1600m) on October 12.

"It is the better option," Ryan said.

"Charlie Boy worked well on the course proper at Caulfield on Tuesday and the Prelude is an easier race for him."

While Cassidy has to wait to get another Group One, Ryan has the chance on Friday night to claim the Moir Stakes at Moonee Valley with Snitzerland to run first-up in the feature sprint.