O’Brien had the choice of five horses trained by his father, Aidan, although only three have a realistic chance of glory.
Battle Of Marengo has been beaten once in six starts, but never when ridden by O’Brien, who believes he has a good chance of following up last year’s triumph with Camelot after winning two recognised trials in Ireland.
He said: “It was very difficult (choosing which horse to ride), but I’ve rode Battle Of Marengo in all of his three starts and I won each time he’s run.
“I think he has a good chance. He’s tough, he’s genuine, he tries hard and he stays well.
“He’s versatile in so far as what way you can ride him and he’s versatile as far as ground goes.
“I do think he’s a better horse on quicker ground but I think he’s as good a chance as any.”
Looking back on Camelot’s win last year, O’Brien admits it was a fairytale experience.
He told BBC Radio 5 Live: “It was a dream come true from the time I was a baby. It was a dream to ride in the race, let alone win it.
“Pressure is a great thing to have because it means you have a great chance of winning the race.”
Dawn Approach is in the same position of Camelot this year having won the 2000 Guineas, but unlike the 2012 hero, there are question marks over his stamina ahead of the mile-and-a-half event.
Bolger only added his unbeaten charge to the Derby field in April and admits Dawn Approach’s staying ability is open to question at this stage.
He said: “If you were to take it at face value, he probably would not get a mile and a half but because he settles so well and he has such a good temperament and he has so much class, he may well get a mile and a half. But we won’t be sure until we try it.
“I will be leaving (tactics) to Kevin (Manning, jockey) but hopefully there will be plenty of pace.
“We need pace to get him to settle early on. We’d be disappointed if we didn’t get pace and after that may the best horse win.”
Asked about whether Dawn Approach would handle the unique atmosphere of Derby Day, Bolger said: “I think he’ll be able to cope with it all right.
“He didn’t get very flustered at Newmarket and I don’t know what factor you would need to multiply the decibels at Newmarket by to replicate Epsom, but I’m sure he’d be able to cope anyway.”
While Godolphin technically have a Derby hero to their credit in 1995 winner Lammtarra, he did not sport their royal blue silks so Dawn Approach would be the first in their famous colours.
Godolphin’s racing manager Simon Crisford said: “Dawn Approach heads to Epsom Downs in fantastic condition.
“He was very impressive at Newmarket and we are very hopeful that he can stay the extra half-mile of the Investec Derby.
“There is a question mark regarding his stamina based on his pedigree but, if he gets the trip, I think that he will be very hard to beat.”
Elaine Burke’s Libertarian is the only British-trained colt without complete outsider status. Despite overturning a disappointing effort in the Sandown Classic Trial by winning the Dante, regularly the strongest trial, he will still comfortably be double-figure odds.
The trainer’s husband, Karl, said: “He’s either good enough, or he isn’t, and he either stays or he doesn’t, but he’s a high-class horse and not the finished article.
“If everything goes well and he handles the track, I can see him running into a place.”
David Wachman’s lightly-raced Galileo Rock has slipped under the radar somewhat considering he had Libertarian behind him when third at Sandown.
“We’re happy with him, he seems in good form and he’s a well-balanced horse,” said Wachman on At The Races.
“We think the longer he goes the better he’ll be, his brother (Saddler’s Rock) gets two miles so he should get the trip.
“The Derby looks a one-horse race, it looks like it’s Dawn Approach’s to lose, after that it’s anybody’s.”
While the British defence is decidedly weak against a strong Irish challenge, momentum has been gathering over the chances of several other overseas visitors.
Andre Fabre brought Pour Moi for a racecourse gallop at a pre-Derby media event ahead of his victory in 2011, and he followed the same ritual with Ocovango, which allowed jockey Pierre-Charles Boudot a first taste of the Epsom undulations.
Like Pour Moi, Ocovango won the Prix Greffulhe at Saint-Cloud, where he has raced exclusively so far.
“They are totally different horses,” said Fabre.
“Pour Moi was a fiery horse with a fantastic turn of foot, this is more of a galloper type.
“It is difficult to assess Ocovango’s form but he is a Derby horse. He has a very good balance and cruising speed.
“There is a slight doubt about him staying because there is a lot of speed on his dam’s side but his sire Monsun is a very strong staying influence so I think he should be OK. He goes on any ground. The race is all about Dawn Approach if he stays but everyone has a chance for places.”
Andreas Wohler saddles a first German-trained runner in Chopin, who was bought by Sheikh Fahad Al Thani’s Qatar Racing operation after victory on his reappearance in a Group Three at Krefeld and supplemented for the race at the start of the week.
Sheikh Fahad said: “After he won at Krefeld, all of our people were impressed, (racing manager) David Redvers was impressed, and I was impressed.
“Particularly this year, where there are lots of doubts about horses staying, I think he has a definite chance of getting in the first four.
“The Derby is the number one goal at the end of the day, it’s the race you want to have a runner and have a proper chance with.”
O’Brien snr is happy with his team of runners, with Battle Of Marengo joined by Ruler Of The World, Mars, Festive Cheer and Flying The Flag.
The Ballydoyle handler said: “So far they’re all good. They did their last canters on Friday and everything seems to be fine.
“You have to get a mile and a half, you have to be balanced and versatile and tough and all the other things that go with it.
“Our horses are well and we’re hoping they’ll run good races. We’ll learn a lot.
“It’s the ultimate for a jockey, trainer, owner and breeder.”