There was a time when Chris Waller started to doubt his credentials as a horse trainer without a Group One win on his CV.

While he had won numerous races on the Australian calendar and had been successful in lesser black-type events, he dearly wanted a win at the highest level.

That was achieved in 2008 when Triple Honour won the Doncaster Handicap at Randwick and since then there has been a steady flow of Group One victories that now total 53.

But it's a win in one of the big four races - the Melbourne Cup, Caulfield Cup, Cox Plate and Golden Slipper - that Waller sees as career-defining.

On Saturday Waller has Kermadec, Preferment and Winx representing the stable in the Cox Plate at Moonee Valley in a bid to break his majors drought.

"Up until 2008 I hadn't trained a Group One winner and I was questioning myself at that elite level," Waller said.

"When we won the Doncaster in 2008 it gave me the confidence and since then we've managed to pick up a lot of races and we haven't changed a thing."

Waller doesn't focus on the fact he hasn't collected one of Australian racing's majors and says that to have one, let alone three runners in a Cox Plate is a privilege.

"I try not to think about it too much," Waller said.

"It's one of those things, just let it unfold and if it happens, it happens, and then you're a part of history."

Waller enters Saturday's race confident he has his three horses in peak condition and says he couldn't be happier with the trio's work during the week.

"They're sound and moving well and a big part of training these days is the mental side," Waller said.

"They're all very calm, bright and happy.

"That's the way to have a horse I feel, just like a sprinter going into a grand final event, keeping it nice and relaxed."