Conversation so far:
What is the Portland Trail Blazers?
Portland Trail Blazers in the 1974 NBA draft.
When did he join the Portland Trailblazers ?
1974 NBA draft and was hailed as the savior of the Portland franchise.
He signed with the Trail Blazers.
Against whom did he play while with the Trailblazers?
Walton returned to action for the playoffs, but was reinjured in the second game of a series against the Seattle SuperSonics.
Did he have any notable wins ?
He nonetheless won the league MVP that season (1978) and the Sporting News NBA MVP, as well.
What did he do after the Trailblazers ?
Walton demanded to be traded, citing unethical and incompetent treatment of his and other players' injuries.

Question: When did he leave the Trailblazers ?
Self-contained rewrite: When did Walton leave the Trailblazers ?