In Pixar's Cars, Smokey is the famous racer who trained Doc Hudson.
Smokey appears in Cars 3 as a resident of Thomasville, the former racing community where Doc Hudson rebuilt his career after leaving Radiator Springs. He explains Doc's earlier years and helps Lightning McQueen understand the training methods and racing philosophy that shaped the Hudson Hornet.
The character is voiced by Chris Cooper and is designed as an old-fashioned pickup truck. Smokey's stories connect Lightning's modern racing problems with the history of the early Piston Cup era. His workshop and the Thomasville setting also introduce several former racers associated with Doc.
Louise Nash and Junior Moon are real characters from Doc's racing past, but they are not the answer to this question. Smokey is specifically the mentor and trainer who worked with Doc after the younger racer sought a new direction.