"They breed them big over there, mate, they just keep coming. If he's anything like their rugby players I'll hit him with all I've got and he'll just keep coming forward.
"It's going to be an entertaining fight. It's a massive challenge. What's the worst that can happen? I get knocked out. At least I tried."
Having taken a first look at Botha with his shirt off, Williams said looks had little to do with effectiveness in the ring.
"He's crafty. It doesn't matter what you look like. Experience is the key ... I think his last four or five fights went the distance. He'll do 12 rounds pretty easy. Hopefully I can up the pace a bit or slow it down - fight it at my pace.
"This is a defining fight for me. If I lose that will probably be it, but if I win it will open a few doors as well."
Two of Botha's last three fights entered the last round. All were losses, however, and one of the more painful would have been a knockout in the 12th round at the hands of Michael Grant in Johannesburg in 2011.
Botha lost both of his fights last year and last tasted victory in June, 2011 against Flo Simba in Gauteng, South Africa.
He fought Holyfield in Las Vegas in 2010, losing by TKO in the eighth round.
Botha was entertaining at the weigh-in. He arrived 10 minutes before Williams and walked around the press conference room in red bandanna and dark sunglasses telling anyone who would listen that he was going to knock out his former All Blacks opponent.
The pair greeted each other with smiles and a handshake, however, which proved it was nothing more than hot air on Botha's part. When asked about Botha's performance, a much more low-key Williams said it was just part of a game he wasn't willing to play.
"I don't have the runs on the board to trash talk anyone in the boxing sense. I've got to do it the hard way and earn that respect."
He added in a hint at his tactics: "I'm a bit faster than him and a bit more nimble. But I won't be running all night."
That will be one of Williams' biggest tests as he prepares for the biggest night of his boxing career - whether he can land punches powerful enough to trouble the compact and experienced Botha. The other part of the equation is of course whether Williams can withstand a series of powerful punches.
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