Brickyard Ride struck the inside rail approaching the eighth pole of Friday's fifth race while racing near the front, unseating jockey Jose Velez.
Brickyard Ride crashed through the rail and fell. He was caught by an outrider and was walked back to the barns.
Velez was quickly on his feet after the fall and walked into the front passenger seat of an ambulance for a mandatory trip to first-aid. He was cleared to ride the seventh and final ride, stewards said.
Velez won two races earlier on the program.
Brickyard Ride, trained by Craig Lewis, brushed the rail for a few strides passing the three-eighths pole, but recovered quickly to race just behind eventual winner Fly the Sky (the 2-1 favorite) around the turn and into early stretch.
Fly the Sky was leading when Brickyard Ride unseated Velez in the stretch. Temporary rails were placed 30 feet from the permanent position for Friday's races on the turf course. Because the temporary rails were the inside rails, they can give way quickly when a horse makes contact.
Independent of that incident, the stewards conducted an inquiry into the opening furlong when Knifes Edge and Leatherneck had to be checked. Knifes Edge was hampered significantly.
There was no change to the order of finish.