Gai Waterhouse has laughed off the fury expressed by More Joyous' owner John Singleton after she declined to select an inside barrier for his mare in Saturday's $3 million Cox Plate (2040m) at Moonee Valley.

Moving to defuse her good friend Singleton's outrage when she picked gate 11 for the champion, Waterhouse said on Wednesday it was simply a case of a "lovers" tiff, that's all."

Singleton said he wanted an inside barrier and was amazed the trainer deliberately chose gate 11.

The pair have been friends for 40 years and, while they have shared many big wins, they have also had disputes over the placement of horses at various times.

Singleton told News Ltd he would have taken drastic action had the trainer been anyone but Waterhouse.

"I love Gai but this is bloody madness," Singleton said. "If this was a normal race and not the Cox Plate, the horse would be scratched and the trainer sacked.

"I instructed my racing manager Duncan Grimley to tell Gai to get barrier four to six if possible.

"Gai didn't need to pick that barrier. It's absolutely ridiculous, no one in the world thinks this is a good barrier."

The Cox Plate is unique in that the horse's name is drawn out first before connections are asked to select the barrier they want.

More Joyous was the first horse drawn and Waterhouse had all 14 barriers to choose from before picking up 11.

Waterhouse on Wednesday defended her decision to select a wider barrier for More Joyous.

"I think she's got a terrific barrier, she's best when she's away from the fence," Waterhouse said.

"She's no good cluttered up.

"Her best two runs of the last year have been the Doncaster and the Queen Elizabeth - in both she drew outside.

"I think it's to her advantage and my job's to win the race."

Waterhouse said she always gave her owners her best advice.

"I've got three horses in it, completely different types of horses and I advised my owners where I felt they should be."

She said she had not yet spoken to Singleton.

"No, but we've texted each other a couple of times and that was good," she said.

"Sometimes when he gets cross with me I think it's best not to ring."

Waterhouse described Singleton as "fantastic".

"He's outstanding. He's the best thing I've ever known - outside (husband) Robbie of course.

"He's got a big picture. He's doing all sorts of promotions. John's the one who will say things and I'll carry them through.

"I find him terribly innovative. I like training for him.

"He get's a bit cranky sometimes - don't we all," she said."

Meanwhile, Waterhouse worked her three Cox Plate runners, More Joyous, Pierro and Proisir, at Flemington on Wednesday morning.

"They're athletes, if they were in a paddock they'd be running around," she said.

"Each of them have done pretty well the same work this morning, they've all trotted and cantered.

"There are two different ways at Flemington on Wednesday and Friday, you can go the Sydney way or the Melbourne way.

"Some of them I've sent the Sydney way just to give them a change and some of them the Melbourne way if I think they need more work on that leg.

"They're all really happy chappies and they're all ready for Saturday in no uncertain terms," she said.