MIAMI - Caroline Wozniacki says it would be "impossible" for her to follow Serena Williams' lead and return to tennis after giving birth.

Williams, the 23-time Grand Slam champion, continues her comeback on Wednesday following the arrival of daughter Olympia when she takes on Japan's Naomi Osaka - winner of the Indian Wells title on Sunday - in the first round of the Miami Open.

Williams is certainly up for the challenge and is determined to roll back the years and return to the apex of tennis.

But close friend Wozniacki, the Australian Open champion and current world No 2, is amazed to see the 36-year-old back on court after 13 months on the sidelines.

"Can I imagine coming back at that age after having a baby? Well, I can imagine it for her," said the Danish star.

"She's such an amazing athlete. She loves to play and I think it's amazing and it's great for the sport. It's great to see her back.

"But I think at 36 and having a baby, for me it would be impossible. I don't think I would be able to keep up with that.

"It's pretty remarkable. She seems the same, though. She's happy and I think you get a different perspective on life when you have a baby."

Miami tournament director James Blake has called on the WTA to rethink its rules after Williams wasn't seeded for the tournament after being way from the tour for more than a year.

"When you come back, you have to start from scratch and it's the same for everyone. But Serena will be fine, she's not worried," said Wozniacki.

While Williams will be fighting to add to her remarkable haul of honors, Wozniacki, who starts her campaign in the second round against either Sam Stosur or Monica Puig, heads into the build-up towards the French Open and Wimbledon full of confidence after finally landing her first Grand Slam championship in Melbourne.