Frankie Dettori will take the ride on John Leeper in Saturday's Cazoo Derby, with High Definition set to miss Epsom.
Dettori had been expected to take the mount of Aidan O'Brien's long-time ante-post favourite, High Definition, but the Irish trainer announced on Wednesday he will instead head to the Curragh for the Irish Derby later this month.
Adam Kirby was lined up for Ed Dunlop's John Leeper, a general 7-1 shot for this weekend's Classic, but has been replaced by two-time Derby-winning jockey Dettori.
Kirby has picked up the mount of 33-1 outsider Adayar for Godolphin and trainer Charlie Appleby.
Champion jockey Oisin Murphy is without a ride, with Godolphin's retained riders William Buick and James Doyle booked for Hurricane Lane and One Ruler respectively.
John Leeper's emotional bid for Dunlop and late father
John Leeper, bred as a son of Frankel out of the trainer's 2010 Oaks heroine Snow Fairy, is named after Dunlop's late father, himself a dual-Derby winning trainer with Shirley Heights in 1978 and Erhaab in 1994.
After spring victories at Newcastle and Newmarket, John Leeper has earned himself a shot at the Classic.
Dunlop told Sky Sports Racing: "It's a great story from an English point of view to have a horse named after my father, who won the Derby twice. Quite rightly people are latching on to it. There's obviously a lot of sentimental reasons for it all.
"There is pressure because of his name, but he doesn't know what his name is.
"The Derby needs a good boost. I'm sure Aidan (O'Brien) will win and have the first four as he normally does but we'll give it as good as we can.
"We'll shed a tear if he wins."
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Dunlop is not hiding the excitement of a first Derby runner since 2016 and his best chance since Native Khan finished fifth in the 2011 edition.
"We haven't had a good horse in a while but this horse has got to go a long way to be as good as his mother," Dunlop said. "It's very exciting, we're lucky to have him.
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"He's very good looking. He's a big, strong horse and weighs over 500 kilos.
"There are very few horses who even have a chance to run in a Derby but this horse is bred to. Not saying he'll win it, but he deserves to be there. At the moment, all roads lead to Saturday."