Doc Rivers says reports he shot down an opportunity to deal away his son, Austin Rivers, for Carmelo Anthony are pure BS ... telling TMZ Sports bluntly, "That's not true."

The Clippers honcho was leaving Madeo in Bev Hills Wednesday night when we asked if Chris Paul's departure meant it was a "sad day" for the team.

"I don't know if it's sad or not," Rivers said ... "We'll find that out."

He praised Paul as a "great Clipper" and added, "I wish Chris well."

We also asked about a report from ESPN anchor Michael Eaves that CP3 left the team upset over issues with Doc ... but Rivers shot that down pretty hard too -- insisting the two are nothing but cordial.