Trainer Tony McEvoy is awaiting a decision from his nephew Kerrin McEvoy whether he will ride talented colt Royal Symphony in the $3 million Cox Plate.

The in-form jockey has been offered the lightweight ride on the colt at 49.5kg in Saturday week's 2040m-feature at Moonee Valley, with the trainer anticipating an answer late on Tuesday.

The trainer and connections of Royal Symphony have decided to give the three-year-old his chance to take on Winx in the country's premier weight-for-age race.

Royal Symphony had to be steadied at the 300m when disappointed for clear running in Saturday's Caulfield Guineas, before finishing fourth.

"We had always said between ourselves that if we won the Guineas we would go to the Cox Plate and he probably should have won the Guineas," McEvoy said.

"The reason he didn't win it was not because he wasn't good enough, it was because he didn't get the opportunity.

"So we've decided that we would still go down that path."

McEvoy, who trained Fields Of Omagh to win the 2003 Cox Plate, said Royal Symphony had come through the Guineas brilliantly.

Kerrin McEvoy won Saturday's $10 million Everest on Redzel at Randwick and the Listed Cranbourne Cup the following day on English visitor, Godolphin's Folkswood, who is among Cox Plate entries.

Champion Winx is the $1.20 favourite to win a record-equalling third Cox Plate and pleased her connections in a gallop at Moonee Valley on Tuesday morning.

Royal Symphony shares the second line of Cox Plate betting at $18 with Caulfield Stakes winner Gailo Chop.