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Rick Fox tells TMZ Sports he's not 100% certain about leaving his wildly successful Esports franchise -- saying he'd stick with Team Echo Fox if they sever ties with a racist investor.

Earlier this week, Team Echo Fox confirmed a minority investor in the Esports franchise used racist language both verbally and in emails. Rick Fox claims he was personally subjected to the racist language.

There were reports Fox -- who founded (and is the face of) Team Echo Fox was leaving the franchise because of that investor.

But, when we spoke with Fox in L.A., the ex-NBA star told us his relationship with T.E.F. could be salvaged ... if the franchise 86s the racist investor from the business.

"I am not looking to go anywhere, but I will not stay in business with a racist," Fox says ... "I just won't."

Fox praised his other business partners, investors, sponsors and players -- but he's drawn a clear line in the sand and now it's up to the T.E.F. to decide what to do.

The issue for Echo Fox ... as Rick points out, the racist investor has rights too.

"The unfortunate thing is being a racist in America is not illegal, unfortunately. He has his own economic interests and his own rights. So, no one is going to trample on his rights."

The stakes are high for Fox -- he's spent years and tons of his own money building Echo Fox into a major force in the Esports world. He's not just a name attached to the team, he's been in the trenches from the beginning helping to build T.E.F. from the ground up.