AIDAN O’Brien has issued concerns over the potential fitness of Australia as the dual Derby winner is pitched into all-aged competition for the first time in the Juddmonte International at York on tomorrow.

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 four rivals lining up, the trainer’s son Joseph is set to slim down to 8st 12lb 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.

Aidan O’Brien said: “He has done very well and is just ready to start back again.

“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 Stoutetrained Telescope and William Haggas’ stable star Mukhadram both proven top-notchers, having finished second and third respectively in the King George at Ascot last month.

Mukhadram had previously claimed a first Group One in Sandown’s Coral-Eclipse, while Telescope impressed in the Hardwicke Stakes at the Royal meeting.

Kevin Ryan’s French Derby winner The Grey Gatsby is an interesting contender, returning to the scene of his victory in the Dante Stakes earlier in the year.

Peter Chapple-Hyam’s Arod has ground to make up on Australia on Epsom form, but is expected to be more effective over a mile and a quarter.

Australia’s stable companion Kingfisher completes the field.

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

Spokesman Paddy Power said: “Joseph O’Brien said after the Irish Derby that he’d love to ride Australia over a mile and two furlongs on fast ground – it might not be quite fast, but it’s close enough and he’ll obviously be a very tough nut to crack.”

  • Royal Ascot winner Baitha Alga stars among 15 juveniles confirmed for the Irish Thoroughbred Marketing Gimcrack Stakes at York on Saturday.

Since opening his account at the second attempt at Chester, Richard Hannon’s charge has claimed impressive victories in the Woodcote Stakes at Epsom and the Norfolk Stakes at the Royal meeting.

Baitha Alga is also entered in the DBS Premier Yearling Stakes on Thursday’s card.

Hannon similarly has Phoenix Stakes runner-up Kool Kompany and Beacon in the same two races.

There is a strong representation from Ireland with Aidan O’Brien’s pair The Great War and War Envoy joined in the list by Tommy Stack’s Accepted and Rapid Applause from Michael O’Callaghan’s yard.

The Peter Chapple-Hyamtrained Ahlan Emarati, Bryan Smart’s Fendale and Karl Burke’s Glenalmond also feature in the Group Two over six furlongs.

  • Dermot Weld’s Pale Mimosa is the remaining top weight on 9st 10lb as a huge field remains in contention for Saturday’s Betfred Ebor.

The defection of Eye Of The Storm and Camborne leaves Weld’s mare, whose three Listed victories to date include the 2012 Galtres Stakes on the Knavesmire, sitting alone at the head.

Among those to be confirmed at the latest stage are the red-hot favourite Pallasator, representing Sir Mark Prescott and now Qatar Racing after their recent purchase of the Ascot winner.

  • Tax Free could not quite finish what he started at Thirsk as the Nicholls family’s star sprinter ended his racing career.

It was in April 2005 that Tax Free made a successful debut at the same track, and in 94 more races he won 17 further times, including four Group races, and finished fourth in the 2009 Nunthorpe.

Now 12, Tax Free was given a round of applause by his local crowd after showing up well but finishing ninth in the Download New Racing UK iPad App Handicap.

He will now be looked after by jockey Adrian Nicholls, who said: “It’s like the end of an era – it seems a lot of has water gone under the bridge since he first came here.

“He owes me nothing and now he can go out in the field with all his pals.

“You’ve got to stop at some point, he’s taken me to some of the best racecourses in the world. It’s sad to see him retire but I wouldn’t want to see him rated 60 and running round the lesser tracks.

“We decided to come here as it’s local, it’s nice to see him finish here.”

The winner was Jim Goldie’s Go Go Green (14- 1) who had been unlucky at Ayr on his previous run.

Jamie Spencer stopped off for a double in the middle of a hectic spell even by the standards of an international jockey.

After riding for boss Sheikh Fahad at Deauville on Friday, the Irishman flew to Arlington to partner Side Glance into third in the Arlington Million and Just The Judge to the same position in the Beverly D, and he will be back in America next weekend.

Spencer’s visit was rewarded when Michael Bell’s 5-4 favourite Banditry held off the runningon Adele by a neck in the Breeders Backing Racing EBF Maiden Stakes.