In Pixar's Cars 3, Lightning McQueen's young trainee who later races for Dinoco is Cruz Ramirez.
Cruz begins the film as a highly skilled trainer at the Rust-eze Racing Center. She is assigned to help McQueen prepare for the challenge posed by Jackson Storm, but McQueen initially resents her methods and the modern training technology. Cruz has racing ambitions of her own, although she has spent years being told that she is better suited to coaching than competing.
During the Thomasville sequence, McQueen recognizes Cruz's talent and encourages her to enter the Florida 500. She eventually replaces McQueen in the race and defeats Jackson Storm. At the end of the film, Cruz becomes Dinoco's new racer, while McQueen continues racing in a new role.
Cruz is voiced by Cristela Alonzo. She is not Sally Carrera, McQueen's partner, and she is not a younger version of McQueen; she is an original character whose story forms the film's central generational handoff.