Kelly Kip, one of Thoroughbred racing's top sprinters, retired on Saturday because of a leg injury.Trainer H. Allen Jerkens, who called Kelly Kip the "fastest I've ever been around," said his horse "didn't walk off too good" after a recent morning gallop. The ailing front leg is the latest in a series of problems to have have sidelined the 6-year-old.Owned by Hobeau Farm, Kelly Kip won 15 of 31 starts with earnings of more than $1.1 million. He set three track records in New York -- Belmont Park (five furlongs), Aqueduct (six furlongs) and Finger Lakes (six furlongs). His eight graded stakes wins include the Frank J. De Francis Memorial Dash Stakes (gr. II), the Forest Hills (gr. II) and A Penomenon (gr. II) Handicaps, and consecutive renewals of the Bold Ruler Handicap (gr. III), in both of which he set an Aqueduct track record. In his last start, he finished sixth in the Forest Hills Handicap (gr. II) at Belmont Park.