Boxers don't come much more durable than Williams, who has never been knocked out in his career, with his only TKO loss coming courtesy of a burst eardrum that forced him to retire in 1999.
Williams, from the Bahamas, has been carefully selected as an opponent for Parker. His handlers want someone who will test the South Aucklander and take him the distance in a bid to get in some valuable rounds. You can spar, train and run all the roads you like but nothing compares to the heat of the battle when the bright lights are shining.
"I feel really fit and strong," Parker said. "I'm mentally and physically in the right place, so I'm definitely ready for the challenge."
Parker's PABA and WBO Oriental heavyweight titles will be on the line at The Trusts Arena and there's a good chance Williams could take Parker the scheduled 10 rounds.
That would also be a first for the Kiwi, given he has never fought past seven rounds.
"If I wasn't comfortable fighting 10 rounds with Sherman, I wouldn't have taken the fight," Parker said.
"In training we do all the hard work so I know that I'm physically ready to go 10 rounds if I have to go 10 rounds.
"We train to fight for 12 rounds so I know that my fitness can take me there."
Parker also said the 42-year-old Williams could expect an improved version of himself, following his latest training camp under Kevin Barry's tutelage in Las Vegas.
"I've got a lot more of a variety of punches to show and I can throw a lot more body shots now. So people will see a little bit of a difference in how I throw my punches and how I mix it up."
His lightning-quick left jab will be one weapon that could hurt Williams.
Parker needed a cortisone injection on Monday to help a problem in his shoulder, which had caused inflammation around a tendon.
"I'm definitely going in to this fight with no worries," Parker said. "I'm not nervous about my shoulder."
Parker received another confidence boost this week after he jumped to No11 in the WBA's rankings.
3 things in Parker's favour
Rankings rise
Parker received a confidence boost this week after he jumped to No11 in the WBA's rankings.
Hard yards
He says he is physically ready to go 10 rounds.
Real weapon
Parker's lightning-quick left jab could hurt Williams.