Breeders' Cup Sprint runner-up Thunderello, who was originally scheduled to enter stud at Doug Arnold's Buck Pond Farm near Versailles, Ky., instead will enter stud at John T.L. Jones Jr.'s Walmac International near Lexington. His fee will be $7,500.Bred in Florida by Four Horsemen's Ranch and raced by Charles Mady, Thunderello finished a strong second in the Napa Breeders' Cup Sprint (gr. I) last October. The son of Montbrook set the pace with fractions of :21.53, :43.91, and :56.09 before being passed by Orientate in deep stretch and finishing a half-length behind him. The final time was 1:08.89. Thunderello had gone into the race off a triumph in the Gallant Bob Handicap in 1:09.83 for six furlongs at Philadelphia Park.In what turned out to be his final start, Thunderello broke a splint bone and chipped a sesamoid bone in his left front leg in the Nov. 16 Frank J. De Francis Memorial Dash Stakes (gr. I) at Laurel. Following the race, it was announced that Mady would stand Thundrello at Buck Pond. Mady later sold Thunderello to the partnership that currently owns him. Thunderello currently is recuperating at Kesmarc, a rehabilitation center near Versailles, Ky., and is expected to arrive at Walmac the end of February.Thunderello retires with three wins and three seconds from seven starts and earnings of $388,400. His victories include a 14 1/4-length maiden win as a 2-year-old at Saratoga. His dam, On the Square (by In Reality), produced two earlier stakes winners. Promising youg sires Awesome Again and Storm Creek appear under his third dam, Square Generation.