He said: "It will be a dream come true to make my debut on Sunday. Every player wants to play in the Aviva Premiership and I can't wait for the match to begin.
"When I arrived in the summer I didn't think I'd be starting against Leicester Tigers at Welford Road but I worked as hard as I could during pre-season and this is a big opportunity so I'm really looking forward to it."
Williams, who is known as a superb lineout technician, captained the Sharks at age-group level in South Africa before deciding to further his career with Tuks and the Pretoria based Blue Bulls.
The lock appeared in all three pre-season friendlies last month and started the matches against both Welsh regions.
And after impressing Director of Rugby Dean Ryan since his arrival from South Africa, Williams says he is ready to make the step-up.
He added: "I had my last year playing at age group level last season. I obviously haven't experienced Aviva Premiership level, which is a big step-up, but after the games in pre-season I know what to expect. So it is a very exciting time for me.
"Leicester's squad is full of international from one to 23 so it's a big challenge for us. My opposite number is Geoff Parling, who was a British and Irish Lion this summer, so I really have to step-up.
"James Percival's injury has obviously opened up a door for me so I will be aiming to take my opportunity."