Terry Thompson, the leading rider of the current Oaklawn Park meet, was injured Saturday after falling from Fleet Boss during the track's fifth race.
Brown Eyed Major came in at the start, bothering Fleet Boss who clipped heels and lost his rider. Brown Eyed Major went on to win but was disqualified and placed eighth.
Thompson suffered a broken thumb and underwent surgery at St. Joseph's Medical Center.
Fleet Boss was not injured in the incident.
Thompson was replaced by Calvin Borel on Chirimoya in the Honeybee Stakes (gr. III) later on the card.