Richie Incognito to Vikings Coach Mike Zimmer, 'You're a F***ing Liar'

Richie Incognito says Minnesota Vikings coach Mike Zimmer is straight-up lying about the NFL lineman's claim that he was talking with the team about a job this offseason ... and it's getting nasty.

It all started when Richie appeared on "TMZ Sports" last week and he told us he'd been speaking with multiple teams about a possible contract ... including Minnesota.

"I'm still in great shape, just waiting on that call. I've had calls from Minnesota, Seattle ... I really just don't want to go to training camp, so we'll see."

Zimmer was asked about Incognito's comments during a press conference on Tuesday -- and straight-up said Incognito was wrong.

"No interest and totally false," Zimmer said ... "Tweet that."

Incognito -- needless to say -- was furious over Zimmer's comments and tweeted, "Mike Zimmer is a F**KING LIAR!!"

Incognito claims he had been talking with Vikings line coach Tony Sparano all summer long and posted screen shots of text conversations. Sparano passed away a few weeks ago.

The screenshots show Incognito was interested in a job -- but they don't show Tony ever made a direct offer. Incognito claims they "spoke weekly this off-season" and believes Tony was seriously interested.