O'Brien told a recent media gathering: "He is one of those very special horses. He is very relaxed, very straightforward and very calm but has a lot of nervous energy."
However, he added: "We are under no illusions with the Derby. We had two very special horses in High Chaparral and Galileo and have not won it since.
"The race is a very difficult test of a horse. There cannot be any chink in their armour and everything has to go right on the day. We are delighted to get there with horses with chances."
O'Brien also races 8-1 third favourite Astrology, an impressive winner last month of Chester's Dee Stakes, a useful Derby trial. Ex-champion jockey Ryan Moore takes the mount.
English trainer Andrew Balding heads the home challenge with 9-2 second favourite Bonfire, who ran an excellent trial when winning the Dante Stakes at York.
Main Sequence (9-1) is a first runner in the classic for trainer David Lanigan.
Unbeaten in his four races to date, the horse faces a much bigger task tomorrow morning.
However, jockey Ted Durcan, confident the colt will last the Derby distance, said: "He'll stay a mile and a half [2.4km] standing on his head and he's on the way up."
Hayley Turner has the ride in the nine-strong field on 66-1 outsider Cavaleiro to become only the second woman to take part in the race after Alex Greaves, last on Portuguese Lil in 1996.
At least Turner will be at Epsom, as opposed to Frankie Dettori whose Godolphin stable does not have a runner this year.
That means the charismatic pilot will be riding at Haydock Park 350km to the north and out of the limelight.
Dettori, 41, bouncy as ever, has said: "Let's get to Royal Ascot [later this month] and see what happens."
Betting: 8-15 Camelot, 9-2 Bonfire, 8-1 Astrology, 10-1 Main Sequence, 16-1 Thought Worthy, 25-1 Mickdaam, 50-1 Rugged Cross, 66-1 Cavaleiro, 66-1 Minimise Risk.Reuters
