LEXINGTON, Ky. — Keeneland says a 2.5% fractional interest in Breeders’ Cup Classic champion Flightline has sold for $4.6 million during a special auction before the start of its November Breeding Stock Sale.

Brookdale Farm’s Freddy Seitz signed the ticket for an undisclosed client, the track announced in a release on Monday. The sale comes a day after ownership of the 4-year-old son of Tapit retired the unbeaten colt following his record 8¼-length victory in Saturday’s $6 million, Grade 1 Classic at Keeneland. Flightline likely locked up Horse of the Year honors with his fourth Grade 1 victory in six starts by a combined victory margin of 71 lengths — dominance that has drawn comparisons to legendary Triple Crown champion Secretariat.

Flightline will begin his breeding career next year at Lane’s End Farms in Versailles, Kentucky, but a stud fee has yet to be determined. West Point Thoroughbreds, part of the bay colt’s ownership, offered the fractional interest. Seitz said the buyer wanted to “make a big splash” and get more involved in the business.

“With a special horse like (Flightline) all you can do is get involved and then just hope for the best,” Seitz said in the release.

“There has never been a horse that has done what he has done for however many years, back to Secretariat. You just have to pay up and get involved, and this is kind of what he’s thinking.”