Despite being 44, Botha, also known as the White Buffalo, is a step up in class for New Zealand heavyweight champion Williams. At the very least he should be able to take a punch, which hasn't always been the case with Williams' opponents.
Botha's record is 48 wins, eight losses, three draws, compared with the undefeated Williams' five wins.
"His experience speaks for itself," said Williams, who is in Auckland seeing family. "For me in a boxing sense I need to take fights like this to move up. It's definitely going to put my name out there internationally if I win because it's for a WBA international belt."
The fight was originally scheduled for last year but was put back due to Williams' chest injury suffered while playing for his Panasonic club in Japan.
Another setback came in the form of the disagreement between his manager Khoder Nasser and former stablemate Anthony Mundine. Mundine's father, Tony, was Williams' trainer but withdrew his services after the bust-up between Nasser and his son. Mahmoud Akkawy, an associate of Nasser and the Mundines, has taken over.
Akkawy said he was impressed with the way Williams had put the injury, which required surgery, behind him.
Meanwhile, Williams wasn't prepared to bite back at Botha's inevitable mindgames, such as "Sonny Bill is a master of the offload but the difference is that he offloads balls whereas I offload punches", and "this is a great opportunity for me, and I am going there to hurt him".
Williams was having none of it. "That's the old-timer coming out in him I guess - the showman. For me it's an honour to fight against someone like him."