Despite being 13 years younger than 35-year-old Williams, Warburton has cemented himself as Wales' first-choice openside - effectively ending his team-mate's international career in the process.
The veteran flanker refuses to glow green with envy though and predicts he won't be the only one struggling to combat the new Wales captain this summer.
"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," he said.
"I can think of easier challenges, but I'm looking forward to it. We've already had a little bit of banter about it.
"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.
"On and off the field he's a model professional.
"Some guys have maybe one or two good games and sit back. He works harder than anybody.
"Defensively he's an animal, he can carry and there's no real weakness to his game.
"He's only going to get better, because the more he plays and the more he learns, the better he is going to get.
"It's quite frightening to think he's just learning the game and how good he is."