Heavyweight contender Andy Ruiz has sent a warning to the critics - and IBF, IBO, WBA, WBO champion Anthony Joshua.
Ruiz is scheduled to face Joshua on June 1 at Madison Square Garden in New York City.
Ruiz is certainly dangerous, but doesn't have an attractive body - while Joshua has a very muscular physique.
Ruiz replaces undefeated Jarrell Miller on late notice.
Miller was removed from the fight after testing positive for several banned performance enhancing drugs.
Ruiz saw action just last month, when he beat down and stopped Alexander Dimitrenko in California. It was Ruiz's debut under the Premier Boxing Champions banner.
The once beaten Mexican-American is confident in his ability to overcome the odds.
"He's a champion of the world," Ruiz told Sky Sports. "There's nothing that I can say bad about him, besides that he's big but you know what, I'm big too and it doesn't really [matter] how big you are in this game. I'm a big fighter, a combination fighter, so I'm here to win.
"A lot of people underestimate me, like I said, the way that I look, my appearance, but as soon as they see me throw punches... I'm going to pull out the upset and June 1 tune in, two big heavyweights bashing their face up, and that's the main thing. Anthony, don't underestimate this little fat boy. I'm coming for you, just tune in man, you're going down."
Ruiz was a frontrunner with several other candidates. He and his team contacted Eddie Hearn, the promoter for Joshua, to get a deal done.
Other boxers on the short-list included Manuel Charr and Agit Kabayel.
"This is my opportunity, my second chance to make history, become the first Mexican heavyweight champion," said Ruiz.
"I've been training really hard, we haven't stopped training. The main thing is to stay focused and stick to the game plan and get that win on June 1. It's kind of overwhelming, everything that happened really fast, but I'm still excited, really happy, really blessed.
"Contacting Eddie Hearn to make the fight, I think I was pressuring him a little bit, but we got the fight done. This is what I wanted and I'm happy that we're here."