Raiders Fan: Donald Penn Is Lying, He Threatened Me First

The Raiders fan who got into it with Donald Penn after Sunday's game claims the NFL star is lying through his teeth -- saying it was Penn who first threatened violence ... and he's got the proof.

TMZ Sports spoke with 27-year-old Sal Chavarria ... who says he only waited for Penn after the game because Penn challenged him to a face-to-face confrontation after some Instagram smacktalk earlier in the season.

Sal admits he was heavily critical of Penn's play on social media -- and was shocked when Penn hit him up in his DM to insult him and challenged him to "say it to my face."

Sal says he did NOT throw a water bottle at Penn during Sunday's encounter, as Penn has alleged -- and claims he has several witnesses to back him up ... including security personnel.

As for Penn's claims that Sal was trying instigate a physical assault in order to shake Penn down for money, Sal says that's BS too ... he doesn't want a cent from the NFL star.

The good news ... Sal says he's such a big Raiders fan, he's open to burying the hatchet with Penn -- if the Raiders ask him to.