Ex-MLB superstar Jose Canseco is boxing a 22-year-old Barstool Sports intern TONIGHT ... and the intern tells us why he's convinced he's gonna BEAT the 56-year-old's ass.
Jose's opponent is Billy Football -- who's VERY confident he can send the former slugger to the canvas when they clash in the main event of Barstool's "Rough N' Rowdy 13" card in West Virginia Friday night.
"I have a very, very competitive side to me that's gonna come out Friday night," Billy tells us.
"I think I'm gonna shock Jose.