Williams, who was named as the region's vice-captain by head coach Wayne Pivac back in the summer, has been deputising for captain Ken Owens whilst he's been absent through injury.
The Scarlets and Wales centre has settled into the role and says he's really looking forward to the festive derbies which includes a massive game against neighbours Ospreys at Parc y Scarlets on Saturday 3rd January. Ahead of this evening's game against Cardiff Blues he said: "I'm really looking forward to next couple of weeks. The support we had here on the weekend was massive.
"We've had a short turnaround this week but the boys are looking forward to Friday.
"One of the goals at the start of the year was to be the top Welsh region - we'll see how that goes over the next couple of weeks.
"It's going to be tough - Blues are a good side with good players. Anything can happen in a derby! We're focusing on carrying our home form away with us.
"It's going to be a tough game and the first time for me playing on the new surface.
"It'll be different but I'm sure they'll have a packed ground. Derbies are normally good games and hopefully it'll be a thriller."
Scarlets return to Parc y Scarlets on Saturday 3rd January to take on Ospreys.
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland