The horse was a mare. I cannot remember any of the stars names. They wanted to put the horse down but the little daughter healed her for her to win the american?? Cup

Is it this?

Dreamer: Inspired by a True Story (2005)

Ben Crane believes that a severely injured racehorse deserves another chance. He and his daughter Cale adopt the horse (a mare) and save it from being euthanized by the owner. The arrival of the mare to Crane's farm will be the perfect opportunity for both father and daughter to reconstruct their lost bond. "Soñador" (Dreamer in English), the renamed mare, despite her broken leg, might have another chance to return to the racetrack with the help of Cale, Ben, and his father, Pop.

Kurt Russell -- Ben Crane

Dakota Fanning -- Cale Crane

Kris Kristofferson -- Pop Crane

Elisabeth Shue -- Lily