Pioneerof the Nile, sire of Triple Crown winner American Pharoah, died unexpectedly on Monday, WinStar Farm has announced. The son of Empire Maker was 13. In a release, WinStar said that Pioneerof the Nile covered a mare on Monday morning, but began acting uncomfortably after he was back in his stall. He was en route to a veterinary clinic when he died. “We are all extremely saddened by the loss of Pioneerof the Nile,” WinStar executive Elliott Walden said in the release. “He was a superior physical specimen, a Triple Crown sire, and a unique personality. All of us at WinStar are heartbroken.” Pioneerof the Nile raced for his breeder, Ahmed Zayat’s Zayat Stables, which bought him back for $290,000 at the Keeneland September yearling sale. He began his career with Bill Mott, winning his maiden on turf at Saratoga in his second start, then finishing third in the Grade 1 Breeders’ Futurity at Keeneland and fifth in the Breeders’ Cup Juvenile at Santa Anita, both on synthetic surfaces. Subsequently transferred to Bob Baffert, he ripped off four straight graded stakes victories on synthetic tracks in California in 2009 – the Grade 1 CashCall Futurity, Grade 2 Robert B. Lewis Stakes, Grade 2 San Felipe Stakes, and Grade 1 Santa Anita Derby. In his first outing on dirt, Pioneerof the Nile finished second in the Kentucky Derby to longshot Mine That Bird, then was 11th in the Preakness Stakes. Retired that summer due to a soft tissue injury, he finished his racing career with a record of 5-1-1 from 10 starts and earnings of more than $1.6 million. Hinting at his future as a stamina-influencing sire, all his victories came at 1 1/16 miles or longer. Pioneerof the Nile retired to Vinery Stud in Lexington, Ky., for the 2010 season. Vinery owner Tom Simon announced in August 2012 that he would put his U.S. properties up for sale, and Pioneerof the Nile moved in time for the 2013 season to WinStar, which stands several former Zayat colorbearers. His first foals began racing that year, and emerging from his second crop was the horse the racing world had been waiting on for 37 years. American Pharoah – who also was bought back as a yearling to race as a homebred for Zayat and was trained by Baffert – swept through the 2015 Triple Crown, winning the Kentucky Derby, Preakness, and Belmont Stakes by a combined 13 1/2 lengths. The 2015 Horse of the Year and champion 3-year-old, as well as the champion juvenile male of 2014, American Pharoah also recorded Grade 1 triumphs in the Breeders’ Cup Classic, Haskell Invitational, Arkansas Derby, Del Mar Futurity, and FrontRunner Stakes. Pioneerof the Nile was represented by another Eclipse Award champion juvenile in Classic Empire, who won the 2016 Breeders’ Cup Juvenile to lock up his divisional title. Classic Empire went on to win the 2017 Arkansas Derby and finish a close second in the Preakness. Pioneerof the Nile’s other standouts include Grade 1 winner Midnight Storm and 2014 Preakness third-place finisher Social Inclusion. Pioneerof the Nile is the sire of 25 stakes winners, with career progeny earnings of $35,152,084 through Sunday. Pioneerof the Nile will have three more complete crops of racing age, including this year’s 2-year-olds. The stallion bred an outstanding book in 2016 – which numbered 120 mares, according to The Jockey Club’s Report of Mares Bred – the year following American Pharoah’s Triple Crown sweep, and is expected to be a major player on this year’s juvenile racing and sales scene. Pioneerof the Nile’s yearling average last season was $352,465, and he was represented by a $1.2 million colt at last week’s Ocala Breeders’ Sales Co.’s March sale of 2-year-olds in training, opening that market calendar. Pioneerof the Nile covered 127 mares in 2017 and 124 in 2018, according to The Jockey Club’s statistics. He was about a month into this season at WinStar, which opened its breeding shed on Feb. 15. He was standing for an advertised fee of $110,000. In addition to his own remaining foals, Pioneerof the Nile has a solid handful of sons at stud to continue his legacy. American Pharoah, whose highly anticipated first crop races this year, and Classic Empire, who entered stud in 2018, both stand at Coolmore’s Ashford Stud in Kentucky. Other sons of Pioneerof the Nile at stud in Kentucky include multiple Grade 2 winner Cairo Prince, who finished third on last year’s freshman sire earnings list, at Airdrie Stud, and Midnight Storm, whose first foals are arriving now, at Taylor Made Farm. “Incredibly shocked and saddened by the sudden loss of my Pioneerof the Nile,” Ahmed Zayat said on Twitter Monday afternoon. “He was not only my first homebred, he was one of my greatest. He was the proud father of American Pharoah and a true sire of sires. Pioneerof the Nile will be greatly missed by all of us here at Zayat Stables, and by all of the racing and breeding world. Thank you to Bob Baffert for training him, thank you to WinStar Farm for standing him and caring for him these last years. He is gone way too soon, but never to be forgotten. It truly does take a Pioneer. My sweet boy.”