Donald Sterling -- HEY BLACK FRIENDS ... Defend Me!

Donald Sterling is desperately trying to play the "I have black friends" card ... problem is, he can't get a black friend on board ... TMZ Sports has learned.

Sources connected to Sterling tell us ... the disgraced L.A. Clippers owner has reached out to several people he considers friends -- hoping they will vouch for him as a not-racist person.

We're told one of the people he reached out to is an African-American basketball player -- who respectfully declined Sterling's request ... along with everyone else Donald reached out to.