Chris Waller has put three-time Group One winner Preferment on notice ahead of the $1.5 million BMW at Rosehill.

"Saturday is going to tell me a lot. If he doesn't win he'll never be tried over 2400 metres again," Waller said.

The trainer is in jockey Hugh Bowman's corner in questioning whether the 2014 Victoria Derby winner can go the distance as an older horse.

"I'm not convinced," Waller said. "I don't care how the race is run.

"Whether it is run at break-neck speed or as a sit and sprint.

"He'll get his chance. He's got a beautiful gate and he's in Group One-winning form."

Preferment has been at the top of betting since nominations closed on Monday as he tries to follow Manighar (2012) and Makybe Diva (2005) as recent horses to complete the Australian Cup-BMW double.

Ridden to offset a slow tempo in the Australian Cup, Preferment was beaten across the line by Awesome Rock before getting the race on protest.

It confirmed his liking for Flemington where he has won his three Group One races.

In two starts on his home track, Preferment is yet to win but he went close in last year's Rosehill Guineas when beaten in a photo-finish by Volkstok'n'barrell.

Bookmakers have Preferment ($3.50) shading Our Ivanhowe ($4.20) for BMW favouritism.

Their only clash since last year's Melbourne Cup resulted in Our Ivanhowe finishing 1-1/2 lengths behind Preferment when fifth in the Australian Cup.

A minor placing last year with 100-1 chance Beaten Up is the closest Waller has come to winning the BMW but he says Preferment is in a different class from a majority of stayers he has sent around in the race.

Waller rates Our Ivanhowe and Caulfield Cup winner Mongolian Khan as genuine threats to Preferment but he can also make a case for his handicap stayers Who Shot Thebarman and Grand Marshal as they take another step towards the Sydney Cup.

"If Who Shot Thebarman and Grand Marshal are going to be winning a Sydney Cup they are going to have to run well in a BMW, which I think they can," he said.

"They are two very seasoned stayers."