2 names come to my mind
Shawn Kemp
1999-2000: 17.8 points, 8.8 rebounds
2000-2001: 6.5 points, 3.8 rebounds
(copy paste from wikipedia)
During the lockout shortened 1998–1999 NBA season, Kemp reportedly showed up to training camp weighing 280 pounds, though Cleveland's then general manager Wayne Embry revealed that he was actually 315 pounds. (...) The last few years of Kemp's professional basketball career were riddled with problems stemming from his weight, as well as cocaine and alcohol abuse. His first season in Portland ended early when he entered drug rehabilitation. Antoine Walker
In all honesty, I wasn't following the games at the time. I bet most of you guys have more things to say than I do. All I've heard is that his game deteriorated quickly since he got traded to Dallas.
Roy hibbert went from all star to out of the league in the span of like 2 years lol
Danny granger also fell out of the league a lot faster than I thought he would
TP! Hibbert is a great example!
Granger had injury problems. I don't think he counts for this one.