The pair will go head-to-head over the weekend in Texas, in a ten-round fight, which is the longest bout in which Paul has ever been involved.
Last time out, Paul knocked Tommy Fury down in the final round of their fight, but he lost by split decision, which was his first career defeat.
This time he comes up against a UFC legend in 38-year-old Diaz and it will be a tough task to come away with a victory, but Paul has made it clear that even if he loses he will not quit.
When asked what he would do if he lost, Paul, 26, told talkSPORT: “I think that’s a decision that is really in the eye of the beholder.
“Mike Tyson says you only fail once you quit and it’s true.
“It’s just a matter of whether I want to do this and having the motivation to be in the gym and make this sacrifice.
“I have so many things in my life, I run a venture capital firm, I run a $300 million sports gaming company, we just launched Betr picks, Most Valuable Promotions – there’s so many other things.
“But, boxing has my heart and I don’t think I’ll ever just hang the gloves up.”
While Diaz has 34 MMA fights to his name, including two against UFC superstar Conor McGregor, this will be his first professional boxing match.
His last fight, however, was in September after which he became a free agent when his UFC contract expired.
Paul, though, also understands another loss would be tough to come back from. “I have to win. Everything is on the line, all the marbles, my career.
“Losing two in a row, you can’t do that in boxing, I have to win.
“I’ve been more motivated than ever and there’s a giant chip on my shoulder to come back and the loss really made me go from a boy to a man and to double down on this sport.
“I had two options, do I really want to do this and run away, or I’m going to come back and never lose again and I chose the latter option.”