The 1970s teen idol has a contender in Mayan King, an undefeated 3-year-old who will run Saturday in the Lane's End Stakes at Kentucky's Turfway Park. Cassidy owns the horse with several partners.
"If I could win the Kentucky Derby, there would be nothing on the face of the earth, other than the birth of my son 14 years ago, to compare to the thrill and the high of it," he said Tuesday by phone from Florida.
The colt is named for a street near Cassidy's home in Fort Lauderdale, Fla.
"The day we bought him I thought he was a Derby horse. It's the only time I've ever high-fived anyone in the sales ring," he said. "I've already turned down quite a lot of money for him."
Cassidy, 54, has bred thoroughbreds since the 1970s, when he rose to stardom playing Keith Partridge on "The Partridge Family" (search). He has used a different name because he didn't want to draw attention to his celebrity.
Trainer Paul Aguirre, who will saddle Texcess on Saturday, remembers Cassidy's teen idol days. "It makes it hard to root against him," he said.
Cassidy can't attend Saturday's race because he's doing a concert at a Connecticut casino that night.
"I'm free May 7," he said, laughing. The 131st Kentucky Derby will be run that day at Churchill Downs.