CM Punk's first MMA fight will come at UFC 203 against Mickey Gall. Getty

CM Punk has never stepped foot inside the octagon, but he’s not short on confidence ahead of his mixed martial arts debut. Less than a month before his first fight at UFC 203 on Sept. 10 in Cleveland, the former WWE champion doesn’t have any doubts about the outcome.

“Honestly, there’s no assuming. I’m gonna win,” Punk told Hot 97’s Peter Rosenberg on Monday. “I’ve never been more confident about something in my entire life.”

Punk will face the relatively unknown Mickey Gall, who is 1-0 in his UFC career. He’ll be fighting nearly two years after signing with UFC, following his abrupt departure from WWE, where he became one of the biggest stars of his generation. But unlike Brock Lesnar, who’s competed in both WWE and UFC, Punk does not have any kind of MMA background.

The 37-year-old is a significant underdog entering his welterweight fight. He began training at Roufusport in Milwaukee in January of last year with the likes of former UFC champ Anthony Pettis and former Bellator champ Ben Askren.

Punk received mixed reactions from the MMA world when he was signed in December 2014. While some fighters welcomed him with open arms, others scoffed at the idea that a professional wrestler would get a shot in the octagon ahead of other UFC hopefuls.

While some fighters don’t begrudge him for using his stardom to get a UFC contract, they remain skeptical about how well he’ll do in his first fight.

"Yeah, I’m curious as to how he’s going to do of course," UFC heavyweight Alistair Overeem recently said on The MMA Hour, referring to Punk’s upcoming fight. "But I think he’s in for a hard time. I don’t know who he’s matched against, but this is definitely different than pro wrestling. Especially in his weight class, he’s a welterweight, I believe — those guys are tough man. He’s going to experience it firsthand. And you know the thing is too? If he does bad, the whole world’s going to be on top of him. If he does good, the next guy will be in line for him, and the next guy is going to just keep on coming. There’s so many good guys at welterweight."

"So, that’s definitely somebody I wouldn’t want to be right now."

Punk is well aware of the challenges that he’ll face at UFC 203, and he didn’t make any major declarations when he signed with the company. But he believes he’s ready to get a win in his first fight.

“I wish it (UFC 203) was tomorrow,” Punk told FS1’s Colin Cowherd. “I will definitely be ready. I’m ready now.

“Nothing concerns me. Nothing’s gonna happen on the 10th that I haven’t seen already. Nothing’s gonna shock me, and 100 percent I will be ready.”