Aidan O’Brien will wait until later in the week before making a final decision on whether to saddle both Puerto Rico and the supplemented Gstaad in the Betfred 2000 Guineas at Newmarket.

Dual Group 1 winner Puerto Rico looked to have assumed the position of the Ballydoyle handler’s number one contender for the Rowley Mile classic after Breeders’ Cup hero Gstaad, along with Albert Einstein, were taken from the race last month – but it later transpired they were scratched due to an administrative error.

While the latter remains an absentee, Gstaad was reinstated at a cost of £30,000 ahead of Monday’s confirmation stage, but O’Brien insists he is not yet a guaranteed runner on Saturday.

Speaking on Monday afternoon, he told the Press Association: “We’re not sure yet. The current thinking was Puerto Rico would go there and Gstaad might go to the French (Guineas), but that’s not 100 per cent sure.

“We’ll see how they are the next couple of days and then decide. It’s very possible the two could go, we’ll see.”

Puerto Rico and Gstaad are two of four O’Brien-trained contenders, with Causeway and Flushing Meadows also on the list of 20 colts still in the mix.

Unbeaten record on the line

Fozzy Stack’s Thesecretadversary and Robson De Aguiar’s Power Blue could also cross the Irish Sea, while the British team is headed by Bow Echo, who will put his unbeaten record on the line over the Rowley Mile.

George Boughey’s son of Night Of Thunder won each of his three starts last season and signed off with a victory in the Royal Lodge Stakes over the Guineas course and distance.

There is a second supplementary entry in Charlie Pike’s Padraig Dawn, who finished second in the Burradon Stakes at Newcastle on just his second career outing.

Charlie Appleby could be double-handed with Dewhurst third Distant Storm and the unbeaten King’s Trail, while Roger Varian’s Avicenna is another possible runner for Godolphin.

John and Thady Gosden’s Oxagon beat Avicenna into second in the Craven Stakes and also stands his ground.

Karl Burke may be triple-handed with Greenham winner Alparslan, Billecart and Hankelow, While Francis-Henri Graffard’s Samangan is the sole international raider.

Needle reversing form?

Into The Sky, a length second in the Mill Reef at the back end of last season, represents Jim Boyle and Needle Match, fourth behind Alparslan in the Greenham, will attempt to reverse the form for William Haggas.

The field is completed by Andrew Balding’s Venetian Prince and Ismail Mohammed’s Lord Britain.

Sponsors Betfred are offering a £2million bonus to any horse that wins the Triple Crown of the 2000 Guineas, Derby and St Leger.

Betfred founder Fred Done said: “It was an honour last year to be the first company in history to sponsor all five British Classics and I can’t wait to do it all again this year.

“That is why I am offering the £2million Triple Crown bonus again. Nijinsky was undoubtedly one of the greats and it is about time we had another Triple Crown winner to celebrate.

“Can another horse rise to the occasion, make history, and do it again?"

£525,000 Betfred 2000 Guineas (Group 1) 1m

Alparslan (IRE) 3 9 2 Mr Mohamed Saeed Al Shehhi K. R. Burke Clifford Lee

Avicenna (IRE) 3 9 2 Godolphin Roger Varian Ray Dawson

Billecart (IRE) 3 9 2 Amo Racing Ltd & Valmont K. R. Burke Rowan Scott

Bow Echo (IRE) 3 9 2 Exors of the Late Sheikh Mohammed Obaid George Boughey Billy Loughnane

Causeway (IRE) 3 9 2 Mr M. Tabor, D. Smith & Mrs John Magnier Aidan O'Brien Ireland

Distant Storm 3 9 2 Godolphin Charlie Appleby William Buick

Flushing Meadows (USA) 3 9 2 Mr M. Tabor, D. Smith & Mrs John Magnier Aidan O'Brien Ireland

* Gstaad 3 9 2 Mr D. Smith, Mrs J. Magnier, Mr M. Tabor Aidan O'Brien Ireland

Hankelow (IRE) 3 9 2 Exors of the Late Sheikh Mohammed Obaid K. R. Burke

Into The Sky (IRE) 3 9 2 Mrs D Tabor, Dr P Wilson & R Stanbridge Jim Boyle Kieran Shoemark

King's Trail 3 9 2 Godolphin Charlie Appleby James Doyle

Lord Britain 3 9 2 Mr Abdulla Al Mansoori Ismail Mohammed

Needle Match 3 9 2 Mr Saeed Suhail William Haggas Tom Marquand

Oxagon (FR) 3 9 2 Prince A. A. Faisal John & Thady Gosden Oisin Murphy

* Padraig Dawn (IRE) 3 9 2 Niall Keating & Gary Gillies Charlie Pike Edward Greatrex

Power Blue (IRE) 3 9 2 Amo Racing Limited Robson De Aguiar Ireland David Egan

Puerto Rico (IRE) 3 9 2 Mrs John Magnier,Mr M.Tabor & Mr D.Smith Aidan O'Brien Ireland

Samangan (IRE) 3 9 2 Aga Khan Studs Scea Francis-Henri Graffard France Mickael Barzalona

Thesecretadversary (IRE) 3 9 2 Cayton Park Stud/Mrs John Magnier J. A. Stack Ireland

Venetian Prince 3 9 2 Mr J. C. Smith Andrew Balding

* supplementary entries

18 confirmations plus 2 supplementary entries

6 Irish-trained

1 French-trained