It's unlikely there was anyone happier than apprentice Jye McNeil to learn Ninth Legion had been scratched from the Sir Rupert Clarke Stakes to run in Sydney.

Ninth Legion's withdrawal from Saturday's Group One Sir Rupert Clarke at Caulfield paved the way for first emergency Petrology to gain a start.

It means 20-year-old McNeil is set to have his first Group One ride.

"I set myself a few goals at the start of the new season to get rides in big races like this one and it's good to be able to achieve that so early in the season," McNeil said.

McNeil has one stakes win to his credit having partnered Taiyoo to a Group Three victory in Adelaide earlier this year.

His booking for the David Hayes and Tom Dabernig-trained Petrology at 52 kilograms in the 1400m handicap is an opportunity the apprentice hopes he can build on.

"Without being able to ride light I wouldn't have had a ride in this race so it's a little advantage for me and I'm glad that David and Tom have been able to give me the opportunity," he said.

"It's a very important time of the year for everyone to see that I can ride light, and if I can ride the horse well and the horse can perform well, it would be a very good time of the year to be in the headlines for sure."

Petrology is at $35 with the TAB's market headed by the Lee and Anthony Freedman-trained Disposition at $3.50.