Li Na said she was stunned by Serena Williams' impressive comeback from giving birth and said her old rival has a golden chance to reclaim her Wimbledon crown.
Li is 36 and a mother like Williams but Asia's greatest-ever player quit the tour four years ago and now concentrates on bringing up her young family.
The 2011 French Open and 2014 Australian Open champion is not tempted to make a comeback of her own, as she watches Williams compete at Wimbledon for the first time since winning her seventh All England Club title in 2016.
"How fit she looks, especially after having a baby. I think she has a very big chance to win the trophy again," the former world number two said.
"I'm surprised she's playing so well. It's very tough, especially for women, to find the balance between your children and tennis.
"After four years, I'm still not trying to come back! Especially for the woman, the body changes a lot. And you have at least four or five months where you can't sleep for the whole night. When the baby cries or moves, the woman always wakes up the very next second, so it's very tough."
Williams is playing only her fourth tournament since taking more than a year out and though she is ranked 181 in the world, the US star was seeded 25th at Wimbledon.
She faces German 13th seed Julia Goerges in Thursday's semi-finals -- the first time she has faced another seed, with all the top 10 tumbling out early.
- Family first -
Few female players have succeeded at Grand Slam level after becoming mums.
Belgium's Kim Clijsters returned to win the 2009 US Open, while Margaret Court and Evonne Goolagong Cawley won majors after giving birth in an era when the physical demands on players were less intense.
Li said she did not miss playing on the tour, but did miss testing herself against the best.
"I live in Beijing. My life is much more relaxed, not like an athlete where you have to put pressure on yourself every second. Now I'm just relaxed, I take care of the family and my husband helps a lot, so that makes it much easier for me," she said.
"I like cooking but I don't like cleaning. We have a nanny who does that.
"I don't really miss the tour but I miss the fighting competition. You don't find that in normal life."
- Chinese rise -
Li is playing with Japan's Ai Sugiyama in the ladies' invitation doubles at Wimbledon.
"I've taken my whole family to London to look around the city, because for them it is the first time in London," she said.
Li has inspired a new generation of Chinese female tennis players and the sport is growing in her homeland, with tournaments and facilities mushrooming.
"It's very good for the players and very good for the fans. For the players, you don't need to have long travelling, you can just stay in the country, you can play big tournaments and come face to face with the top players," said Li.
Wang Xinyu (seeded fourth), Wang Xiyu (seeded 10th) and Zheng Qinwen got through to the last 16 of the Wimbledon girls' singles on Tuesday and Li has been running an eye over them.
"When I saw the three Chinese juniors play over these last couple of days, they way they hit the ball is so fast. I'm not strong like them!" she said.
Li Na takes her seat in the Royal box on Centre Court at Wimbledon on July 7.
Serena Williams celebrates breaking serve during her quarter-final against Camila Giorgi.
Spectators watch as China's Wang Xinyu returns against Argentina's Ana Geller.