13) Spencer Haywood
Hall of Famer Spencer Haywood has mostly been forgotten but he was a dominant center in both the ABA and NBA. He started his career with the Denver Rockets in the ABA and averaged an incredible 30 points and 19.5 rebounds, winning Rookie of the Year and MVP all at the age of 20 before making his way to the NBA and joining the Seattle Supersonics.
Over a five-year span, from 1971 to 1976, Haywood put up monster numbers, averaging a stellar 24 points and 12 rebounds. After that, however, his production became increasingly spotty. He had down seasons in New York, followed by a bounce-back season in New Orleans, before being dealt to the Lakers.
There, he backed up Kareem Abdul-Jabbar, but a drug problem led to his being released during the 1979 playoffs. That sudden release and Abdul-Jabbar's injury led rookie Magic Johnson to start as a center and score 42 points, 17 rebounds, and 9 assists in a series-clinching win in Game 6 of the 1980 NBA Finals.
He would play just two seasons after that in the NBA but was dominant enough during his ABA and early NBA careers to make the Hall of Fame. Still, had his career not been derailed, he would likely have had a bigger name.