Jim Cassidy had already won the VRC Oaks four times before James McDonald was born.

That puts the longevity of Cassidy into perspective as he prepares for his final day of race riding at Thursday's Oaks meeting at Flemington.

"Is that right?" the 23-year-old McDonald responded when told Cassidy had won the Oaks in 1986, 1987, 1989 and 1990.

Cassidy added another in 2012 on Dear Demi and will team again with trainer Clarry Conners and owner John Singleton with Dawnie Perfect on Thursday.

McDonald will be among his rivals when he rides one of the favourites, Ambience.

"He's been a great servant to the sport and deserves all the credit he can get," McDonald said about Cassidy.

"His record speaks for itself. If anyone could have half as good a record as him, they'd be happy."

But McDonald will be doing his best to deny Cassidy a Group One-winning finish, confident Ambience has the credentials to give him a first VRC Oaks after her impressive Wakeful Stakes win on Saturday in which Dawnie Perfect finished fourth.

"She got to the big course at Flemington on Saturday which was a bonus and the rain won't hurt her if it comes," McDonald said.

"She's a pretty good filly. She feels like she's an out-and-out stayer. Her form suggests that and you couldn't say she was stopping on the line on Saturday.

"She'll be there."

McDonald has won a New Zealand Oaks, a Queensland Oaks and an ATC Australian Oaks in Sydney.

Clarry Conners has won the Oaks with Research (1988), Arborea (1993) and Dear Demi.

He believes Ethereal Stakes winner Dawnie Perfect has a genuine chance to give Cassidy a final top-level win.

"He'll be riding it like a demon, his last day riding," Conners said.

"I'm pretty keen on my filly. We don't want a wet track I don't think. On Saturday she was on the worst part of the slow lane. She's more a dour type of horse.

"I've been waiting to get to Flemington with her for the Wakeful and the Oaks because I think she'll stay all day."

Cassidy has four rides on Thursday with Dawnie Perfect to be his second last.

If she can win, Cassidy will retire with 105 Group One wins but whatever happens, he says the time is right.

"I'm happy. It's the right decision," he said.

"I'll just look forward to Thursday and enjoy it."