Wow, hate to label anyone as an underachiever, but a couple of guys who were denied a more substantial career because they died young were Nick Vlahos of the Northeast and Tony Ellin of South Carolina. The more obscure but celebrated Boy Bikol, a Filipino superstar who influenced Efren Reyes, was murdered. Some say he played better than Efren. All three are "might-have-been" players.
A player from the late 1990's was denied his chance by a condition that ended his career. By the age of eighteen, he was already starting to be counted among the most elite. He was Michael Coltrain of North Carolina, a protege of Johnny Archer. He's a "might have been" along with others who had conditions or ailments that obstructed their careers as pro pool players.
Others may also have had the talent to have had greater success, but full-time jobs made it impossible for them to reach the very first tier of professional pool achievement. One such guy was Jack Colavita, a craftsman/machinist from New Jersey, once voted by his peers (on the PPPA tour in the early 1980's) as having the best stroke in the game despite the presence of guys like Mizerak, Rempe, Sigel, Varner and some others. Jack is, consequently, a might have been" as are many others like him.
Another MONSTER who died young, Steve Gumphries, from Baltimore.