Maurice Stokes was a freakishly good player in the early days of the NBA but his career only lasted three years.
In one of the greatest tragedies in NBA history, Stokes hit the floor in the final regular season game of his third season and passed out. Things seemed fine but after his only career playoff game, against Detroit, he told his teammates he felt extremely sick. Then he had a seizure and was permanently paralyzed. He was later diagnosed with post-traumatic encephalopathy.
It was a brutal career-ending injury for the talented Stokes. Keep in mind that in that era, not only were salaries limited - JJ Redick was partly correct when he said that early NBA players were “plumbers,” but it was more out of economic necessity - but they also didn't have a pension.