Martina Hingis - still the youngest Grand Slam champion in Open history - has marveled at the way women's tennis has changed since her ascent to stardom as a teenager.

The Swiss star reached all four major finals as a 16-year-old in 1997, only missing out on the title at Roland Garros.

"I was the youngest in most of the things I did," Hingis, now 36, told CNN. "Now, I look back at it and see [today's] juniors and young upcoming players ...You say, 'Oh, Jelena Ostapenko, when she won the French Open she was only 20 years old!'

"And I'm like hang on...Back then when you were 20, if you hadn't won a grand slam by then you were almost too old!"

Anna Kournikova and Martina Hingis win the Australian Open in 1999 (Getty)

Hingis also discussed the overall pattern of play in matches, indicating a preference for strategy over strength on the court.

"Sometimes I did complain that I want to see a bit more variety and a little bit of strategy in the game," she added.

"You see that more in the men's tennis, but eventually women will return to that. Once you are able to control that power, [you] have the variety out there again. Sometimes I think that's forgotten. 'Hey, tennis is a game. It's not just sheer power!'"

Hingis is enjoying a renaissance in her career after returning to tennis, following two spells in retirement.

Since her return in 2013 she has won 13 additional doubles Grand Slam titles - including two in two days at this year's US Open, becoming women's doubles champion with Chan Yung-Jan and mixed doubles champion with Jamie Murray.

That brings the 36-year-old's overall tally in singles and doubles to 25 Grand Slam titles.