Giant's Causeway is 7 to 4 favourite to go one better than when runner-up at Newmarket in Saturday's Entenmann's Irish 2,000 Guineas.
Two of the three supplementary entries made yesterday, Barathea Guest and Bachir, appear to be Giant's Causeway's main dangers.
Godolphin, in addition to the French 2,000 Guineas winner Bachir, also supplemented the ex-German horse Glad Master for another £25,000.
The three additions mean 10 horses are left in the first Irish Classic of the season although the other O'Brien entry, Bach, is more likely to wait for the Group One Prix Jean Prat at Longchamp on Sunday week.
"Most likely Giant's Causeway will run on his own. He's in good form," said O'Brien yesterday.
Although Barathea Guest has a length and a half to make up on Giant's Causeway from Newmarket, his trainer, George Margarson, is encouraged by the likelihood of give in the ground.
Godolphin also splashed out £25,000 to put the Newmarket maiden winner Meiosis, a daughter of Danzig, into Sunday's 1,000 Guineas. Lahan attempts to complete the English-Irish Guineas double and will start favourite. The Michael Grassick-trained filly Preseli looks the main threat.
Aidan O'Brien has five of the 16 left in the fillies Classic and describes Amethyst and Chiang-Mai as his most likely runners while Dermot Weld confirmed Pat Smullen will ride Theoretically in the race, in addition to Legal Jousting in the 2,000. The German 1,000 Guineas winner Crimplene was the other supplementary for the race.
The mighty Montjeu domiantes the nine entries for Sunday's Tattersalls Gold Cup but the field was expanded by Godolphin's decision to supplement the St Leger winner Mutafaweq to the race for £12,000.
Meanwhile, the ground conditions may not be ideal for the return of the Ascot Gold Cup winner Enzeli in tonight's Saval Beg Stakes but it will still be a major surprise if that is enough to stop John Oxx's Group One performer from beating just four opponents.
Enzeli won this race last year on route to springing a 20 to 1 upset at Royal Ascot but even allowing for his SP and a subsequent fourth of five in the Irish Leger, let no one doubt Enzeli's class.
First of all pulled muscles in his back explained his very poor Leger effort and there is no way to describe his Ascot victory as anything else but first rate. Nedawi, Celeric, Kayf Tara and Invermark, all Group One winners, were devastated by Enzeli's burst of foot on fast ground.
