I'd go with Marvin Barnes. But, it's only a 6 year sample, and not the at least 7-8 years suggested as a sample size. But he belongs on the list of tremendous squanderd talent, IMO. Drafted 2nd, behind Bill Walton, by the 76's in 1974. Instead he signed with St. Louis of the ABA, played 2 years, and then just 4 more in the NBA. A young announcer named Bob Costas was the announcer for St. Louis. I can only agree with Costas' opinion. I do believe he could have gone as far as a player as he wanted to go. But, he didn't, and toward the end of his life, he returned to the drugs that had derailed him originally. Marvin "Bad News" Barnes.
https://www.bostonglobe.com/sports/...-what-waste/cSySkkPcHZaswmWuEZSIPL/story.html
"Marvin averaged 24 points and 15 rebounds a game as a rookie, the Spirits games being broadcast by a 22-year-old announcer out of Syracuse named Bob Costas.
“The epitaph on Marvin?” inquires Costas. “Squandered talent. Extraordinary talent. Hall of Fame talent. Maybe — maybe — all-time great talent. I saw him go for 35 and 25 in games against Dr. J and be the best player on the floor.”
He was even more memorable off the court.
“He had a Rolls-Royce,” says Costas. “He would drive around and pick up kids. He would pull up to the arena, maybe having swung by McDonald’s and picked up a quarter-pounder and some fries, swagger into the area 15 minutes before game time with the kids behind him, have the coach look at him ruefully, and get 40.”