The 18-year-old driver, who replaces Brazilian veteran Felipe Massa in the team's lineup, is set to be the first Canadian to start a Grand Prix since Villeneuve retired in 2006.
Villeneuve, who won the world championship in his second season at Williams, said: “I don't know if you have pressure when you are 18 or 19. I don't think you realise. The pressure comes later when you actually realise what you are getting into.
“At 18, 19 you are still playing even though you're doing it professionally,” he added. “It's not the same kind of pressure. The pressure is there if there's a chance of you not having a career out of it which is not really a risk for him.”
Stroll won the 2016 Formula Three title and follows in the footsteps of 19-year-old Dutch sensation Max Verstappen, a race winner with Red Bull in his second season.
The Canadian's career to date has been financed by his billionaire father Lawrence, who made a fortune from the Tommy Hilfiger and Michael Kors fashion brands.
Williams has said it has every confidence in the youngster, who won his junior championship in October with four races to spare, emphasising that he earned the place on merit.
Villeneuve, who has underlined in the past that money is no substitute for talent, said Stroll certainly had the potential and time would answer other questions.
“We know he's quick but we don't know what his mettle is,” said the Canadian. “We don't know when the going gets tough, and it will, what will happen. How will he react psychologically? That's the only thing we don't know.
“He's with a good team, Williams is a good place to start. He will be well looked after and he can really become good. All we know is he's been quick so we'll see. The opportunity is there. It's too early to criticise him.”
Stroll joined Williams in 2016 as a development driver and has been 'fully immersed' since then in the same way that current Finnish race driver Valtteri Bottas was before joining.
He has already spent plenty of time in the team's simulator and began a track programme in August using a 2014 car.
Villeneuve agreed that Verstappen, who has become a fan favourite with his overtaking skills and refusal to be cowed by anyone's reputation, had set a benchmark and opened the door to other young talent.
Frenchman Esteban Ocon, who beat Verstappen to the 2014 F3 title and turned 20 in September, will be racing for Force India in 2017 as another example of the youth wave sweeping the sport.
‘Times have changed’
“Look at Verstappen,” said Villeneuve who made his grand prix debut at 24. “He wasn't Formula Three champion and look at what he's doing now. The whole environment has changed and you don't need the same big background any more to perform in Formula One.”
Villeneuve, son of the late Ferrari favourite Gilles, also caused a sensation when he made his race debut in 1996 as a fast, fresh and free-spirited talent refusing to bow to convention. But he was already proven at the highest level outside Formula One, winner of the 1995 Indianapolis 500 and US CART series.
His arrival in Formula One, following in the footsteps of his swashbuckling father, was big box office in Canada just as Stroll's debut is likely to be in 2017 at his home race in Montreal.
“You can see it in the way the people are reacting. Canada was needing it so I really hope he'll step up,” said Villeneuve. “He's got a good base and now he just needs to step up to what F1 is.”
Original source: New teen can handle F1 pressure - Villeneuve