Getty Images Kevin Durant

In 1970, NBA legend Oscar Robertson filed a class action suit against the league along with 13 other players, including Celtics great John Havlicek and future U.S. Senator Bill Bradley. Similar to the case brought against MLB the same year by Curt Flood, which eventually reached the Supreme Court, Robertson's lawsuit challenged the NBA's limitation on player movement through the reserve clause. Oscar Robertson v. National Basketball Association was settled in 1976, paving the way for the "Oscar Robertson Rule" and free agency.

The NBA still has means to discourage unfettered player relocation: A restricted free agent's team can match any offer for him, and any team with a player's Bird Rights can offer a larger contract than any other suitors. That's why max-level stars rarely leave on their own accord: Even when they do, some will try to arrange sign-and-trade deals to lock in that larger contract.

But there have been exceptions over the years. And in the last couple seasons, the NBA has seen two of its generation's greatest players take the path less traveled, in search of a greater reward.

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