The 22-year-old has impressed Pivac this month, after starting GUINNESS PRO12 clashes against Welsh rivals Cardiff Blues and the Ospreys.
And the Scarlets boss believes Lee is ready to capitalise on his potential and cement himself as one of the competition's best tight-heads over the coming year.
"Samson is certainly developing into having a very, very big future in the game," Pivac told Wales Online.
"He understands what is required at scrum time. I think he has got a great mentality for scrummaging. He wants to scrum and he enjoys it.
"He has taken ownership for getting it right, so he's done very well.
"There have been plenty of props across the world that have come through at a young age. It's the ones that kick on who become great props.
"He has got a level head on his shoulders. He doesn't get carried away with things and I think that is one of his strengths."
And the New Zealander conceded Lee's form has not come as a surprise - seeing as the youngster already has nine Wales caps to his name.
He added: "I knew he was an international tight-head, so we expected good things.
"He was slow starting because he obviously had that suspension, so he was a bit underdone at the start of the season when he came back into the side.
"But he's improved as the season has gone on and I think the scrum has just got better and better."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland