Classic dilemma: Johnny Murtagh, who partnered Mastercraftsman to victory in the Irish 2,000 Guineas on Saturday (left), has yet to decide which horse to ride at Epsom
The flat, wide-open spaces of Newmarket's Rowley Mile contrast markedly with Epsom's unforgiving undulations and camber.
O'Brien thinks Rip Van Winkle, who suffered an interrupted preparation before the mile Classic, will take it in his stride, however.
He said: "You can never be sure if they will handle the track at Epsom but he is very classy and I don't see any reason why he won't."
As the guessing games continue, William Hill are offering 100-1 that O'Brien saddles the first five home in the Derby and just 5-1 that he trains the first three. He has nine entries from the 20 that remain.
