Frankie Dettori set to ride Aidan O’Brien’s Irish Derby winner Santiago in the St Leger at Doncaster

Frankie Dettori is being lined up to ride Aidan O’Brien’s Irish Derby winner Santiago in the Pertemps St Leger at Doncaster a week on Saturday.

O’Brien needs all his riding team for the Irish Champions meetings at Leopardstown and the Curragh next weekend where his British-based No 1 jockey Ryan Moore will also ride after entering a two-week quarantine period.

That leaves Dettori poised to mount the 11-4 second favourite for the final Classic of the season.

Frankie Dettori is being lined up to ride Irish Derby winner Santiago in the St Leger this month

O’Brien said: ‘We have spoken to Frankie and he is going to be there for the Leger which is great for us so hopefully he will ride some of ours. I imagine we will have to use British jockeys as we need the lads here.’

Dettori won the 2005 St Leger for O’Brien on Scorpion.

O’Brien has ruled Irish Derby runner-up Tiger Moth out of the St Leger. He was prominent in the ante-post betting but will probably run in the mile and a half Kilternan Stakes at Leopardstown with O’Brien doubting he has stamina for the mile and three-quarters St Leger.

O’ Brien could also run Irish Derby third Dawn Patrol and Mythical in the St Leger.

Since his Irish Derby win Santiago finished third to Stradivarius in the Goodwood Cup over two miles.

O’Brien said: ‘Goodwood maybe did not work as we would have liked. We usually like to take our time on him but he hit the gates and Ryan couldn’t get him back. He was sitting in second position maybe in a gear too high all the way.

‘Because of that he went from travelling well and having to ask him to go and race and he really didn’t get his breath to go again. But it didn’t do him any harm and he seems in good form again.’