International Star scratched from Kentucky Derby due to cracked hoof

— -- LOUISVILLE, Ky. -- International Star has been scratched from the Kentucky Derby, because of a quarter crack in his hoof, leaving 18 horses to run for the roses.

Churchill Downs stewards say the colt was scratched Saturday morning, hours before the race was set to be run at 6:34 p.m. ET.

"I am sad to announce that International Star has a quarter crack in his hoof and has been scratched form the Kentucky Derby," tweeted Ken Ramsey, who owns the horse with his wife Sarah.

International Star topped the point leaderboard that determined the 20-horse field for the Derby. He is trained by Mike Maker and was to be ridden by Miguel Mena.

The Ramseys are one of the sport's leading owners and breeders. Five of the couple's horses set to run Saturday were scratched, including three in the Woodford Reserve on the undercard.

They have three others set to run, including Thankyou Marylou in the Humana Distaff and Luck of the Kitten in the American Turf.

The No. 1 spot in the Derby starting gate will be left open and all the other horses will move over so there are no gaps in the gate.

International Star is the second Derby horse to be scratched. El Kabeir dropped out Friday because of a sore foot. Earlier in the week, the owners of Stanford decided not to run their colt.

Quarter cracks are a common cause of foot lameness in horses. They can lead to instability, inflammation or infection.

The Associated Press contributed to this report.