A pile-up at the Del Mar Thoroughbred Club racetrack sent one jockey to the hospital and forced a horse to be put down Friday evening.
Racetrack officials say during the sixth race around 6:45 p.m., the horse called "Yes She's Usual" broke her leg and fell, taking her rider Brice Blanc.
Two other horses crashed into "Yes She's Unusual," and all three jockeys ended up on the track.
Blanc, who fell beneath the horses, was taken to Scripps La Jolla Hospital for a possible broken arm and concussion.
The other two riders were evaluated at the track and were deemed to be fine.
Track officials decided to euthanize "Yes She's Unusual," a 4-year-old filly, because of her leg break.
"Everybody here at the racetrack is feeling terrible about that. It is absolutely the worst part of our game," said Mac McBride with the Del Mar Thoroughbred Club.
She is the fourth horse to be put down just seven days into the season, and the second one on Friday alone. Another horse was fatally injured in the seventh race.
Last year, nine or ten horses were euthanized after leg injuries. This year's season runs until September.
When asked if the injuries may be connected to something with the track, McBride said it's doubtful.
One horse was racing on grass and the other on the main track, he said.