There are not many players who know more about the 22-year-old than Williams, who has seen him rise through the ranks at Cardiff Blues and on the International stage.
Battles between the duo are usually limited to competing for a starting berth for club and country but on June 4 they will line-up against each other for the first time and veteran Williams can’t wait.
“It is going to be an interesting one,” he told the Western Mail.
“I wish I was a few years younger taking him on to be honest with you, but I’ll enjoy it, I can’t wait.
“I’m going to have my hands full with him, there’s no doubt about that. I’ve probably learned more off him than he has off me, he’s that good.
“I can think of easier challenges, but I’m looking forward to it. We’ve already had a little bit of banter about it.
“It will be very strange and there is no doubt there will be a bit more banter during the game.
“He’s a great athlete and such a strong, physical bloke.
“But it’s the top two inches with Sam as well. He analyses the game really well and always wants to improve. He’s a great bloke.
“He keeps his feet on the ground and he’s going to be a huge star – a British Lion a number of times.”
In addition to his 98 Caps for Wales and four for the British and Irish Lions, Williams has made five appearances for the Barbarians in his career, the first coming back in 1998.
He has the opportunity to add to that tally this weekend when the famous invitational side play England at Twickenham before traveling down to Wales and Williams has admitted he had to take some time before committing to play against his country.
“I got asked during the Six Nations,” he added.
“They said, ‘Look, if you are not involved in the summer, would you like to tour with us against England and Wales?’
“I did have to think about it for a while. It’s a bit strange playing against Wales.
“But loads of boys have played against their countries for the Barbarians.
“When I sat down and really thought about it, I reckoned it would be a nice way to finish off at the stadium, playing for the side I started my international career against.
“So it was an initial thought of ‘Shall I do it?’ but then I jumped at the chance.
“When you look at the list of players in the squad, you never turn that opportunity down.
“It’s something different, but I’m really looking forward to it and it should be a great day.”
“All the years I’ve been playing, my Barbarians weeks have been some of the best highlights I’ve had.
“I’ve played for them on four or five occasions and it’s always been a huge honour.
