Ballydoyle chief Aidan O'Brien has confessed that Mastercraftsman is likely to prove best at a mile.

The Irish 2000 Guineas and St James's Palace Stakes winner has been campaigned over 1m2f on his last two outings, finishing second to Sea The Stars in the Juddmonte International at York.

He was then third behind the same horse - and stablemate Fame And Glory - in the Irish Champion Stakes.

"Johnny (Murtagh) wasn 't sure at York whether he hadn't got the trip or just got tired in the last half a furlong. Leopardstown was a little bit like that as well," the trainer had to admit.

"A real searching mile-and-a-quarter isn't for him. He's probably a miler who get a mile really well and we can let him use his stride.

"His best run, most impressive ever, was six furlongs on good to firm ground at the Curragh when he won the Phoenix Stakes by over four lengths

"There's no doubt he's all speed but his lazy demeanour and the way he races sucks you into thinking he'll get a mile-and-a-quarter. A flat ten furlongs mightn't be a problem on a fast surface but we felt at York he got outstayed or tired. Then at Leopardstown a forceful mile-and-a-quarter looked maybe a little too far for him."

Mastercraftsman remains as low as 15.5 (Betfair) on the exchanges to land the Breeders’ Cup Classic in November, a victory that would cap a memorable season for the colt.