LEXINGTON, Ky. – Veteran jockey Robby Albarado underwent surgery Monday at University of Kentucky Hospital for a compound lower-leg fracture he suffered when thrown from his mount several strides out of the starting gate during the eighth race Sunday at Keeneland. The setback will sideline Albarado for an undetermined period and will force him to miss his ride on J Boys Echo in the 143rd Kentucky Derby at Churchill Downs. Albarado was injured when his mount, Chiltern Street, broke awkwardly from the inside post in the 5 1/2-furlong turf allowance. Albarado fell off to the right side of his mount, landing feet first. No other horses or jockeys were involved. Keeneland track physician Barry Schumer, who observed Albarado before the 43-year-old jockey was transported to the hospital, said the injury apparently occurred because of the way Albarado landed and not because the jockey was struck by his mount. Jason Boulet, a longtime close friend of Albarado’s, said the affected area is the tibia and fibula, just above the left ankle. Keeneland officials initially said the injury was to his ankle. The untimely injury means Albarado will be unable to ride J Boys Echo, the winner of the Gotham Stakes for the Albaugh Family Stable and trainer Dale Romans, in the May 6 Derby. Among Albarado’s other scheduled stakes mounts was Kentucky Oaks contender Daddys Lil Darling, a fast-closing second in the recent Ashland Stakes at Keeneland. The injury comes nearly six years after Albarado suffered a facial injury that led to him being taken off his scheduled mount in the 2011 Kentucky Derby on the eventual winner, Animal Kingdom. The injury was not serious enough for Albarado to miss other mounts on the Derby card, but the connections of Animal Kingdom opted to replace Albarado with John Velazquez. Boulet, the racing secretary at Fair Grounds in New Orleans, described the latest injury as a “pretty ugly break” while attesting to Albarado’s determination to recover and return to riding. “It’s very disheartening to him,” said Boulet. “He is like my brother. We’ve been through a lot of highs and lows together. I have never known anyone with such a strong will.” Albarado has won 5,046 races in a career dating to 1990. He is best known as the regular rider of Mineshaft, the Horse of the Year in 2003, and Curlin, the Horse of the Year in 2007 and 2008. He was nominated this year to the National Museum of Racing and Hall of Fame but did not get elected. Albarado was also the regular rider of Not This Time, who was retired with a lower-leg injury shortly after finishing a fast-closing second last fall in the Breeders’ Cup Juvenile for Romans and the Albaughs. Romans, who is personally close with Albarado, obviously will need a new jockey for J Boys Echo, most recently fourth in the April 8 Blue Grass Stakes at Keeneland. “Nothing’s easy,” said Romans. A regular rider at the major Kentucky tracks while making his primary residence in Louisville for the last two decades, Albarado has ridden 14 times in the Derby without a win. His best finishes were a second on Golden Soul (2013) and a pair of thirds on Steppenwolfer (2006) and Curlin (2007). Albarado recently parted ways with his longtime agent, Lenny Pike Jr., and is now represented by Ronnie Ebanks. Ebanks said Monday that the surgery went well, with a rod and two screws implanted in the tibia. Ebanks added that Albarado might be able to return to riding in three to four weeks.