By 1957, when Tevis was writing "The Hustler", which was first a short story published in Playboy in 1955 I think, good ol Rudy Wanderone was already settled down with a wife and living in Illinois. He hustled quite a bit in NY back in the 1930's, even moved to Virginia during WWII to hustle servicemen in Norfolk. But after the war he moved back to Illinois. If Tevis ever saw or met him it would've been very brief while Rudy was on the road hustling, either in NY City or in Lexington KY near Tevis's home town.
After The Hustler was published, Wanderone read the book and immediately saw an opportunity to make a buck. He was a hustler. He started spreading the word that the character in the book was him. When Tevis heard that there was a fat pool player claiming to be "Minnesota Fats", he told his wife he was going to sue him for using the name as means to make money. But he never did sue Wanderone, probably because there wasn't much of a case.
Nevertheless, most everyone that knew Tevis knew that he was an avid pool player when he was younger, not great, but good enough to hustle locals in surrounding towns before he become an English teacher and started writing short stories. I'm sure he saw plenty of fat pool hustlers, probably even heard rumors of a guy dubbed Double Smarts or Triple Smarts or New York Fats. Tevis visited NY quite often, but during those years
Rudy was living in Illinois, semi-retired, making occasional road trips with a buddy when he could.
Rudolph Wanderone wasn't "the greatest hustler in the world" until he adopted the name "Minnesota Fats" from Tevis's book, and then after the movie came out it paved him a future straight into stardom. The fictional character, Minnesota Fats, played by Jackie Gleason in the movie, was more than likely a composite of several real life characters that Tevis had either seen in action or heard about during his years of playing pool. And now the name of this fictional character, Minnesota Fats, is more popular among non pool players than any real worldclass player has ever been, living or dead.