Williams is aware of the challenge as he vies for the vacant WBA International heavyweight title.
"It's a massive risk but it's massive reward as well," Williams said.
"I know who he is, I know where he's been but that's the challenge.
"I could lose. That's the element of risk you have to take.
"All my career that's what I've done - put myself out of my comfort zone and take risks.
"I'm 27 now - I'm not getting any younger. It's either all or nothing.
"If I want it to come to fruition - the dream of doing this in the future - I need to do this."
Williams wasn't always convinced he was up to taking on a fighter of Botha's class, but gained confidence from his last-start win over Clarence Tillman.
Williams stopped Tillman in the first round of their bout in Hamilton last February.
"Before (the last fight) I didn't think I had too much ability," Williams said.
"I just tried to use my athleticism.
"It was a real eye opener. I just seemed to pick it up.
"It surprises the heck out of me. Boxing's not in my blood.
"My old man probably threw a couple of overhand rights in the pub but that was it," he joked.
Williams credits Tony Mundine with developing his ring acumen but, after his manager Khoder Nasser's fallout with Anthony Mundine prompted a change of cornerman, he continued under the tutelage of Mick Akkaway.
"We sought out Mick's help and it has grown from there," Williams said.
"My confidence has grown. That's why we're stepping up in calibre of fighter."
Williams admitted his pectoral injury, which delayed the bout from its original November date, had hampered his training slightly but insists he is now fully fit.
"I saw the specialist last week and its 100 per cent," Williams said.
"I could have pulled out of the fight again but I don't want to be outside the ring for two years."
After attacking Williams' credibility on Tuesday, Botha (48-8-3, 29 KOs) was in a far more polite mode, insisting the movement of rugby players such as Williams and Quade Cooper into boxing is beneficial to pugilism.
"I wish more sportsmen would come into the boxing arena," Botha said.
"It is really reviving boxing."
Botha has lost four of his past five bouts and hasn't fought since his points loss to Italian Francesco Pianeta in Germany last year.
- AAP
