The FanSided guide to horse racing: What is a filly?

There won’t be any fillies in the Kentucky Derby, but they will race in the Kentucky Oaks on Friday.

“Filly” may be a term that is specific to racing, or really the horse world in general, but the concept is simple. A filly is just a female horse that is less than four years old. As racehorses begin (and often end) their careers before their fourth birthday, most female racehorses are fillies.

Like most professional sports, horse racing is separated by gender. Well, in some ways. Races don’t actually specify that only male horses (colts, stallions, and geldings) can compete. But they do say that only female horses can compete in their races. Limited competition, and the belief that fillies don’t develop as strong physically (though that may not be true) mean most stick to their own gender.

Some of the best fillies have competed against the boys in big races, and acquitted themselves admirably. In 2009, the mare Zenyatta took an undefeated record into the Breeders Cup Classic against the boys and kept it intact. She almost repeated the performance in 2010, but fell a head short.

Also the phenomenal filly Rachel Alexandra won the Preakness Stakes, Haskell and Woodward Stakes in 2009. She became the first filly ever to win the Woodward (which is against older males). Also, in that campaign she beat the winners of both the Kentucky Derby and the Belmont Stakes. So who knows what would have happened if she tried for the Triple Crown.

Next: 20 short stories about the 2018 Kentucky Derby horses

Though the Kentucky Derby is technically open to fillies, they have a hard time gaining the points necessary to qualify. Over the race’s 144 year history, 39 have run, and 3 of them came out with a win: Regret, Genuine Risk, and Winning Colors. This year’s field will not include any fillies. The story is similar for the other Triple Crown races. Fillies can enter, but relatively few do so. Rachel Alexandra was the fifth filly to win the Preakness, and the 53rd to run in 2009. Twenty-three fillies have run in the Belmont, and again, three have won it, most recently Rags to Riches in 2007.

There won’t be any fillies running in the main event on Derby Day, but they get their own event the day before. The Kentucky Oaks, which takes place on Friday, May 4, is the girls’ stand in for the Derby. It is not nearly as widely known or watched on a national scale, but Oaks Day is one of the best attended events of the racing calendar. It gives the girls time to shine.

For more from the Triple Crown, starting with the Kentucky Derby, make sure to follow FanSided and stay tuned to our horse racing hub for all the latest news and results.