Andre Rison is going to bat for Jon Gruden ... telling TMZ Sports he knows the former NFL head coach is definitely "not a racist."
Rison -- who played for Gruden and the Raiders in the 2000 NFL season -- said despite the vile, racist, homophobic and misogynistic words Jon wrote in emails from 2011 to 2018 ... he still believes the guy is a good man.
"We all say some things behind closed doors that we regret or we wouldn't say in public," said Rison, who's remained close to Gruden even after the '00 season ended.