Champion and classic sire Uncle Mo was euthanized on Thursday following a leg injury. The stallion, who resided at Coolmore's Ashford Stud in Versailles, Ky., was 16. Owner Mike Repole, who was introduced to the nation when Uncle Mo became his first Grade 1 winner and champion, said the son of Indian Charlie underwent surgery yesterday for an injury to his left front leg – the nature and cause of which were not disclosed by either Repole or Coolmore. "Unfortunately, this morning the recovery process was too much for him to endure," Repole wrote on social media. The Repole Stable family, [trainer] Todd Pletcher family, and the entire Coolmore family are heartbroken. "Uncle Mo was so much more to me than a champion and iconic stallion – he was and always will be a part of my family," Repole continued. "Uncle Mo is the patriarch of Repole Stable. There will never be another horse that makes me feel or will impact my life the way that Uncle Mo has." Uncle Mo, by Indian Charlie and out of the Arch mare Playa Maya, was bred by D. Michael Cavey, DVM, in Kentucky, was a $220,000 Keeneland September yearling purchase by Repole. The colt won all three of his starts as a juvenile in 2010, bursting onto the scene with a 14 1/4-length debut romp at Saratoga, then winning the Grade 1 Champagne Stakes by 4 3/4 lengths and the Breeders' Cup Juvenile by 4 1/4 lengths. He was subsequently voted the Eclipse Award champion 2-year-old male. Uncle Mo won the Timely Writer Stakes to start his 3-year-old season, but incurred his first loss when finishing third in the Grade 1 Wood Memorial. He was subsequently treated for a gastrointestinal tract infection, and inconclusive symptoms forced him to be scratched from the 2011 Kentucky Derby the day before the race. In early June, his connections reported he had been diagnosed with cholangiohepatitis, an inflammation of the bile passages and adjacent liver. The colt recovered with treatment, and made his first start in well over four months in the Grade 1 King's Bishop at Saratoga, finishing second by a nose to Caleb's Posse – who went on to win the Breeders' Cup Dirt Mile. Uncle Mo returned to the winner's circle with a three-length score over older foes in the Grade 2 Kelso. In what was scheduled to be his final race before retirement, he finished 10th in the Breeders' Cup Classic. Uncle Mo stood his entire career at Ashford, and got off to a flying start as the leading freshman sire of 2015, establishing what was then a record bankroll in the category. His son Nyquist followed in his footsteps with an unbeaten Eclipse championship campaign that year, capped by the Breeders' Cup Juvenile. He went on to win the 2016 Kentucky Derby. Nyquist went on to be the leading freshman sire of 2020 himself, with champion and Juvenile Fillies winner Vequist in his own first crop. This year, Nyquist sired Juvenile Fillies winner Immersive, the favorite to earn a divisional title at next month's Eclipse Awards. Nyquist is among several successful sons of Uncle Mo at stud; Outwork and the late Laoban both also sired Grade 1 winners. Uncle Mo sired another classic winner when Mo Donegal, owned in partnership by Repole, won the 2022 Belmont Stakes. Nyquist and Mo Donegal are among their sire's 114 career stakes winners through Dec. 18. Those also include Golden Pal, a two-time winner at the Breeders' Cup, and Grade 1 winners A Mo Reay, Adare Manor, Arabian Knight, Bast, Dream Tree, Gomo, Kingsbarns, Mo Forza, Mo Town, Outwork, Unbridled Mo, and Yaupon. In addition to his successful sons at stud, Uncle Mo has also been emerging as a broodmare sire at a relatively early curve – his oldest daughters are 11. His daughter Sataves is the dam of Thorpedo Anna, the favorite to be voted 2024 Horse of the Year. He is also the broodmare sire of Grade 1 winners Geaux Rocket Ride, Howard Wolowitz, and Muth. "We’re all still in shock,” Coolmore's Dermot Ryan said in a release. “He will be greatly missed by everyone here, in particular by his personal groom Rene Macias. He was an exceptional sire both on the racetrack and in the sales ring. I would like to thank Mike Repole for giving us the opportunity to stand him in the first instance and for being a truly fantastic partner, Todd Pletcher for training him to perfection, the Coolmore partners for placing such faith in him and our loyal clients for their unwavering support over the years. “I would also like to thank Dr. Barry David, Dr. Bob Hunt, and Dr. Cole Sandow of Hagyard for their efforts to save him, along with all the team here at Ashford for the excellent care they afforded him throughout his time here," he added. :: Want to learn more about handicapping and wagering? Check out DRF's Handicapping 101 and Wagering 101 pages.