Jon Gruden could lose his job over his 2011 racist email ... so says Raiders legend Tim Brown, who claims firing the head coach is on the table for Las Vegas owner Mark Davis.
"If Mark thinks that there's a problem here, Mark will make a move," Brown said over the weekend during an interview with "SiriusXM NFL Radio," according to the Las Vegas Review-Journal.
"That's how serious Mark is about this kind of stuff. Mark is not going to play this racist stuff. He's not going to allow this stuff to happen."
In a 9-year-old email that Gruden sent to a Washington Football Team exec ... Gruden used racist language to criticize NFL Players Association president DeMaurice Smith.
"Dumboriss Smith has lips the size of Michelin tires," Gruden wrote.
Gruden -- who was an analyst for ESPN at the time -- has apologized vehemently for his language ... but has insisted there were no racial undertones to it.
Instead, Gruden claimed he was just trying to use a different wording of "rubber lips" -- a phrase he says he often uses to describe liars.
Regardless, Brown said he could see Davis bringing out the axe and starting a search for a new head coach over Gruden's words.
"He loves Gruden," Brown said of Davis, "but he loves things being right more than he loves Gruden."
For his part, Brown defended his former head coach -- who he played for with the Raiders from 1998 to 2001 -- saying he does NOT believe the 58-year-old is a racist.
"The way I talk about Gruden, people think he's my dad or something because I have that kind of admiration for him," Brown said.
Gruden said Sunday he has yet to speak with the NFL over the email ... but the league did say it is investigating it all.