Not many people have the balls to threaten Rob Gronkowski -- but TNA star Robbie E is going after the NFL star -- claiming Gronk stole his wrestling nickname and now he's gotta pay!!!
Robbie says he's frickin' livid over a wrestling-style promo Gronk made this week in which he calls himself, "Robbie G" -- accusing Rob of the worst thing anyone can be accused of ... blatant rip-offery.
"I never thought an NFL player from the New England Patriots Rob Gronkowski would have to try and steal my name bro," Robbie says.
"So here's the deal ... I'm gonna beat you worse than the Dallas Cowboys are gonna beat you bro."
Robbie says he's already locked up the perfect place for the two to throw down -- TNA's Impact Wrestling.
Gronk's always wanted to be a wrestler ... so, stay tuned on this one.