The Ballydoyle handler saddles four runners in the Group Three Derrinstown Stud Derby Trial, with Idaho the most prominent in the betting for the Classic at Epsom on June 4.
O’Brien said: “Idaho was second in the Ballysax Stakes at Leopardstown last month.
“He ran quick and well from the back and got to the front, but he got tired in the last 50 yards and we think he has progressed since then.”
Ballysax third Beacon Rock and Lieutenant General also represent Coolmore, while O’Brien expects Shogun - the mount of Ryan Moore - to come into his own over a longer trip after having finished third on his comeback in the Craven Stakes at Newmarket.
He said: “Shogun is a smart horse - he ran well in the Craven.
“He was unlucky not to be second. We think when he steps up to a mile and a quarter he’s going to improve.”
Ventura Storm, who does not hold a Derby entry, caught the eye when victorious in the Feilden Stakes at Newmarket and makes the trip to Ireland for trainer Richard Hannon and owners Middleham Park Racing.
Middleham Park’s racing manager Tim Palin said: “He never does anything flashy - he’s not the type that burns up the gallops and he doesn’t scream ‘Group horse’ to you at home - but he’s got some very decent form in the book.
“When Ryan (Moore) jumped off him at Newmarket he said it was time to step him up to a mile and a quarter, so that is what we are doing.
“He’s the type that just keeps finding and whether he’s a Listed or a Group Three horse, we don’t know, you can only find out on the track.
“We have to tackle the might of Ballydoyle, and it looks like Idaho is the best of Aidan’s, but our other option was to go to France for the Prix Greffulhe and that looked red hot.
“We’re delighted to pit our wits against the likes of O’Brien, Dermot Weld and Jim Bolger.”
Weld is responsible for Tirmizi, who is as low as 16-1 for the Derby after winning so well on his sole start at Leopardstown in October.
Bolger and owners Godolphin are double-handed with Ballysax fifth Moonlight Magic and Saafarr.