Flatter, a consistently successful sire who carried on the legacy of A.P. Indy as a cornerstone of the Claiborne Farm roster for nearly two decades, was euthanized on Monday due to the infirmities of old age. He was 23. Flatter, by A.P. Indy and out of Praise, was a second-generation homebred for Claiborne and longtime partner Adele Dilschneider, and a full brother to graded stakes winner and successful sire Congrats. Flatter won four of his six career starts, and was third in the Grade 2 Washington Park Handicap at Arlington Park in his final start. He retired to Claiborne for the 2004 season, and remained there his whole career. To date, Flatter is the sire of 692 winners from 892 starters – an outstanding 78-percent strike rate – and, led by 67 career stakes winners, his progeny have earned in excess of $84.1 million. His average progeny earnings are $94,297 – an outstanding figure even against his 2022 stud fee of $35,000, and more noteworthy considering that his fee ranged from $5,000 to $30,000 for more than half his career. "Flatter was the kind of sire you'd like to have 10 of," Claiborne's Bernie Sams said. "He was solid and consistent year in and year out. He started at the bottom and worked his way up to being a successful and respected stallion. He was popular among people who bred to race, and was a successful commercial sire as well." :: DRF BREEDING LIVE: Real-time coverage of breeding and sales Flatter’s runners are led by an Eclipse Award champion in West Coast, the outstanding 3-year-old male of 2017 after scoring Grade 1 wins in the Travers and Pennsylvania Derby and finishing third in the Breeders' Cup Classic. He was second in both the Pegasus World Cup Invitational and Dubai World Cup early the following year. Flatter was known for siring runners who held their form over multi-year campaigns, such as two-time Grade 1 Jockey Club Gold Cup winner Flat Out, who also won the Grade 1 Cigar Mile and earned more than $3.6 million; millionaires and multiple graded stakes winners Kobe's Back, Plainsman, and Upstart; and millionaire Lucy's Bob Boy, who won 11 stakes over seven seasons of racing. He is also the sire of Grade 1-winning millionaire Taris; Grade 1 winner Search Results, last year’s Kentucky Oaks runner-up who just added the Grade 2 Ruffian to her résumé on Sunday; Canadian champion and classic-placed runner Avie's Flatter; and multiple graded stakes winners Apart, Classic Point, and Tar Heel Mom. Flatter’s sons at stud include Upstart at Airdrie Stud, who is having a breakout spring with his second crop, including Grade 1 winner Zandon, third in the Kentucky Derby on Saturday, and multiple graded stakes winner Kathleen O. Flat Out now stands in Oklahoma after beginning his stud career in Kentucky, and is now a leading sire in his adopted state. He is the sire of Grade 2 winner Pacific Gale and Grade 3 winners Chateau and Flat Out Speed. West Coast, standing at Lane’s End, is part of the 2022 freshman sire class. Flatter is also the broodmare sire of Grade 1 winners Juju’s Map and Taiba, Grade 2 winner Merneith, and others. "Flatter's passing leaves a huge hole in all of our hearts," Claiborne president Walker Hancock said. "He was a homebred of ours that was tough as nails until the day he passed. He was a farm favorite and will be sorely missed. We will look for his legacy to continue through his sons at stud."