Lankan Rupee and Deep Field have a mortgage on Lightning Stakes betting but jockey Craig Williams is not conceding defeat with Brazen Beau.

Williams rides Brazen Beau in a race for the first time at Flemington on Saturday and he says the Group One sprint looms as an intriguing contest.

"I'm on the horse that's going to be out the back who is going to be stalking," Williams said.

"Looking at the horse's best performances there is no doubt that he's a very good chaser."

Lankan Rupee is the reigning Australian Horse of the Year with four Group One wins while Deep Field is unbeaten in five starts and gets his first chance at Group One level.

Brazen Beau has stamped himself as a quality colt, winning the Coolmore Stud Stakes against a field of top three-year-old's at Flemington last spring, but has yet to meet older horses or raced at weight-for-age.

He is set to embark on his final racing campaign which is scheduled to include a trip to Royal Ascot, before retiring to stand at Darley Stud in Victoria.

Fastnet Rock is the last three-year-old to claim the Lightning after his win a decade ago.

Brazen Beau is on the third line of betting at $5 with Lankan Rupee ($2.30) shading Deep Field ($2.40) for favouritism.

Williams rode Brazen Beau in a soft trial last Friday, won impressively by Deep Field, and said he was a quality galloper.

"Last year Lankan Rupee was the highest-rated sprinter so you have to respect him and his straight form," Williams said.

"Deep Field is undefeated, so they are definitely the two that are on everyone's mind, especially the way Deep Field trialled down the straight the other day. He looked like a rocket.

"But my horse has got a great chance in the race. You can't rule out a horse that was that impressive in the Group One Coolmore."

Free-running Fab Fevola, the outsider of the six-horse field, has been scratched from a 955-metre race at Moonee Valley on Friday night to try his luck in the Lightning.