Pettis and Diaz have always had a simmering rivalry, but the former UFC lightweight champion believes that the 30-year-old crossed the line when he criticised him for getting injured after losing his title to Rafael dos Anjos at UFC 185 in March.
Pettis, who suffered a fractured orbital bone during his fight against dos Anjos, insisted that he has had enough of Diaz's trash-talking and believes that it is time they settle their feud.
"He's not relevant at all, but it's personal," Pettis told MMA Fighting. "When someone talks crap to me in my face, I need to address that. Where I grew up, that doesn't happen. He just talks s***.
"When I walk past him, he has something to say. In Mexico City he had a few words, but it was by the media event. He runs over, gets on the camera and stays relevant.
"I don't play into that. If he wants to fight, let's set it up. I'm not afraid to fight this dude. He's not even top ten. It doesn't make sense for me but the fact that it's personal is why I want that fight. I want to whoop his ass. That's it."