One of the competition's most dynamic players, the 29-year-old departs United for the second time after re-joining ahead of the 2019-20 season.

The American shooting guard helped United win their first title in 2018 - Prather's third-straight NBL championship after winning two with league juggernaut Perth.

Prather had brief stints in Greece and Russia before returning to Victoria last year on a two-season contract with United.

But with the COVID-19 pandemic placing uncertainty around the 2020-21 season, United on Thursday announced Prather's departure.

"Casey is a fantastic player and an even better person, we have loved having him here at Melbourne United," club chief executive Vince Crivelli said.

"However we, like everyone, are having to adjust to new conditions and as such some of our plans that were in place required reassessment."

"New rules, such as salary cap changes and a different limit of imported players on each team, resulted in both parties agreeing that this was in everyone's best interest."

"We will long celebrate Casey's achievements both for our club and more broadly here in the league for years to come and we support Casey with his next career move."

United signed Japanese star Yudai Baba in July after he impressed at last year's FIBA World Cup.

Australian Associated Press