Trainer Aidan O'Brien has issued concerns over the fitness of Australia as the dual Derby winner is pitched into all-aged competition for the first time in the Juddmonte International.

Since being narrowly beaten into third by Night Of Thunder and Kingman in the 2000 Guineas, the son of Galileo and Ouija Board has blown away his opponents at Epsom and the Curragh to confirm himself the leading three-year-old over middle distances.

With just five rivals at York on Wednesday, the trainer's son Joseph is set to slim down to 8st 12lb (56kg) to keep the partnership intact.

This, though, is the likely odds-on favourite's first outing since winning the Irish Derby on June 28 and his team have later targets in mind.

"He has done very well and is just ready to start back again," Aidan O'Brien said.

"I suppose, because he has done so well, we are a little bit worried about his fitness.

"But really, when you give a horse a break, especially a three-year-old, going into the autumn, you want him to do well. He did well, he did very well."

However, just two older horses have turned up, with the Sir Michael Stoute-trained Telescope and William Haggas' stable star Mukhadram who finished second and third respectively in the King George at Ascot last month.

Mukhadram had previously claimed a first Group One in the Eclipse Stakes while Telescope impressed in the Hardwicke Stakes at the Royal meeting.

French Derby winner The Grey Gatsby, Arod and Kingfisher complete the field.

Coral offer 8-13 about Australia ahead of Telescope at 9-2 and Paddy Power are the same price about the favourite.