Rivers was leaving Mr Chow this weekend -- when we asked if his opinion on the fight changed now that we know Blake had been drinking in the hours before he attacked Matias Testi last month.
Rivers shook his head 'no' -- and then went to bat for the NBA star ... saying, "He's a grown man ... and he's a good guy."
It's another big endorsement for Griffin -- who appeared to have the support of NBA commish Adam Silver last week ... who also defended BG as a "good guy."
Earlier in the week, Rivers called for people to forgive Griffin by comparing him to a former U.S. president ... saying, "You have to forgive people at some point. I believe that. We built Richard Nixon a library.”