Doc Hudson is Lightning McQueen's mentor and racing crew chief in Pixar's Cars.
Doc begins the story as Radiator Springs' judge and a secret former champion. After recognizing Lightning's potential and immaturity, he takes responsibility for teaching him about patience, teamwork, and the importance of respecting other racers.
Doc's racing identity, the Fabulous Hudson Hornet, connects him to the real Hudson Hornet stock car. Hudsons were successful in early NASCAR competition, especially during the 1950s, and the film uses that history to give Doc's past a strong automotive foundation.
Doc becomes Lightning's crew chief during the climactic Piston Cup race. Their partnership is separate from Mack, Lightning's transport truck, and from Luigi and Guido, who help with tires and pit work. That distinction makes Doc the specific answer for mentor and crew chief.