French Open: Papa Novak Djokovic hails super-mom Serena Williams

With his daughter Tara born a day after Serena Williams gave birth to her first child Alexis Olympia last September, Novak Djokovic has been trading parenting tips with the American.

However, when he was asked if it's easier to be a tennis-playing father than a continent-hopping mother on the professional tour, the Serb's jaw appeared to hit the floor.

With an incredulous look that seemed to suggest "you cannot be serious!", Djokovic remained mum for several seconds.

But with an expectant audience still waiting for an answer, father-of-two Djokovic finally broke the pregnant pause.

"Well, I think it's obvious. I mean, what a woman has to go through, with the pregnancy and birth and then everything after that? I'm sorry to all the guys, but it's much more difficult for a woman," Djokovic told reporters at the French Open on Wednesday.

"So that's why it makes it even more impressive when they make a comeback, and especially Serena after all she has done," added the Serb, one of a dozen fathers to have claimed Grand Slam titles since 1980.

Over the same period of time, only Kim Clijsters has managed to win majors after returning from a maternity break.

But while Clijsters had won only one of her four majors before giving birth to daughter Jada in 2008, Williams had claimed 23 Grand Slam titles.

Many believe she could have easily called it quits after becoming a mother as she has already cemented her place among the all-time sporting greats.

But rather than walking away from tennis, Williams, who won the 2017 Australian Open while pregnant, is making her Grand Slam comeback at Roland Garros this week.

"It's not like she never won a slam and then now she wants to come back because she has something to achieve from that perspective," added the 31-year-old Djokovic, who was photographed cradling a beaming Alexis Olympia on the eight-month-old's Twitter feed.

"After all she has achieved in sport to see her back and putting hours on the court and work and again and again, it's impressive. It's inspiring. It really is.

"She's the greatest female athlete of all time, probably, and she keeps on coming back and inspiring everyone. She uses tennis as a platform to do good things and that's why she's back. You can see how much she loves it.

"I love Serena. All the superlatives and beautiful words that you can think of she deserves it."