Jockey John Velazquez underwent emergency surgery Saturday afternoon to remove his spleen as the result of a spill he took in the Breeders' Cup Juvenile Fillies race.
Velazquez was riding Secret Compass in the fourth race when the horse broke a front leg and went down. Velazquez was thrown forward to the ground.
The horse was euthanized on the track because her injury was not repairable.
Velazquez was taken to Huntington Memorial Hospital in Pasadena and was set to be released when doctors discovered internal bleeding.
He then was taken into surgery, according to a Santa Anita spokesman.