Standout sire Flatter, considered the cornerstone stallion of Kentucky’s famous Claiborne Farm, was euthanized May 9. He was 23.

The farm announced Flatter was euthanized “due to the infirmities of old age.” That ended a nearly 20-year stallion career that far outstripped his racing career.

“Flatter was the kind of sire you’d like to have 10 of,” Claiborne Farm’s Bernie Sams said in a statement announcing Flatter’s death. “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. He will be greatly missed.”

Flatter ran only six times in his career, opening his ledger with a fourth in a Churchill Downs maiden special weight in June 2002. He broke his maiden next out at Churchill Downs, which kick-started a four-race winning streak.

Flatter never won a stakes race

Flatter won two more allowances at Arlington Park and Turfway Park, before adding an allowance optional claimer at Churchill for win No. 4. The streak ended in July 2003 with a third in the Grade 2 Washington Park Handicap at Arlington Park. After that, Flatter retired to Claiborne Farm for the 2004 breeding season.

There, Flatter made his mark. He sired 696 winners with combined progeny earnings of more than $85 million. He sired 67 stakes winners and 21 graded stakes winners.

Leading that parade was West Coast, the 2017 Eclipse Award winner as Champion 3-Year-Old Male. West Coast won that year’s Travers and Pennsylvania Derby and finished third in the Breeders’ Cup Classic. He also finished second in the Pegasus World Cup and Dubai World Cup, retiring with earnings north of $5.8 million.

Flat Out was a flat-out stud

Not far behind was Flat Out, who banked more than $3.6 million through two Jockey Club Gold Cup victories, a third in the Breeders’ Cup Classic and a farewell score in the Cigar Mile.

Three other Flatter progeny won Grade 1 races: Taris, Paola Queen and Search Results, the 2021 Kentucky Oaks runner up to Malathaat. Search Results opened her 2022 campaign winning the Grade 2 Ruffian Stakes last weekend at Belmont Park.

Seven Flatter offspring banked more than $1 million: West Coast, Flat Out, Taris, Upstart, Kobe’s Back, Plainsman and Lucy’s Bob Boy, an 11-time stakes winner.

Even a Canadian Champion on the pedigree chart

Flatter also sired Avie’s Flatter, Canada’s Champion 2-Year-Old of 2018. He hit the board in all three Canadian Triple Crown races the following year. And as a broodmare sire, Flatter’s daughters produced Grade 1 winners such as Santa Anita Derby winner Taiba and Juju’s Map and Grade 2 winner Merneith.

Flatter was the son of A.P. Indy, the grandson of 1977 Triple Crown winner Seattle Slew and the great-grandson of the iconic Secretariat. He was out of the mare Praise and a great-grandson of Northern Dancer on his dam’s side.

“He was a homebred of ours that was tough as nails until the day he passed,” Claiborne Farm President Walker Hancock said. “He was a farm favorite and will be sorely missed. We will look for his legacy to continue through his sons at stud.”