O'Brien hasn't had a horse compete yet in the U.S. Triple Crown events, though he is the trainer of Giant's Causeway, who just missed winning the Breeders' Cup Classic at Churchill Downs last November.
Aidan O'Brien has submitted the names of 21 horses for the Triple Crown this year, the Irish News reports. Among the 3-year-olds under consideration are group I winner, Minardi, leading Two Thousand Guineas hopeful Hemingway, and Epsom Derby hopeful Galileo.