Former world number one Kim Clijsters believes Serena Williams will get back to the top, but warned it may take time for her to regain full strength after childbirth.
Williams will play her first Grand Slam for more than 15 months at the French Open after having her daughter, Alexis Olympia. She has played just two events since she first returned to the Tour in March.
"Pregnancy is very hard to (come back from),” Clijsters told Reuters in an interview. "Everything is a lot looser, it takes time to get that back to where it once was.
"I remember doing an interview when Serena was pregnant and people were asking me constantly, do you think she can do it? My thing was, you don’t know how your body will react, how you will react emotionally.
"I admire both Serena and Venus because they have a perseverance that is incredible. They’re able to do a lot of things that other people can’t do, physically and mentally, so I don’t doubt that she will come back, I don’t doubt it, but it just takes a little bit of time.”
Clijsters, who is working as an expert summariser for Eurosport and Eurosport Player, who will be broadcasting Roland Garros from May 27 to June 10, retired from tennis in 2007.
She returned to the sport in 2009, a year and a half after having her first child, Jada.
Then 26, Clijsters enjoyed a hugely successful return, winning the U.S. Open in just her third event back and then going on to win two more Grand Slams to take her career tally to four.
Williams has been working hard with her coach, Patrick Mouratoglou, at his academy near Nice, balancing her training regime with her new family life.
Clijsters said getting back into the old routine may have had a rejuvenating effect on Williams.
"Every body reacts differently,” she said, of the physical demands.
"Having a baby is emotional and physically very draining – at times you’re on a high, at times you’re low.
"I fell in love all over again with the sport and I enjoyed taking those few hours off from home to go and work out and play tennis, because I needed it, for various reasons, not just because I wanted to get back into shape.
"I’d just lost my father at the start of 2009 and for me it was a mindset, to get away from it and just focus on tennis. Then I would come home, I’d be with Jada, we’d do family things and I felt like my balance was good and I needed it."
Williams will play Kristyna Pliskova of the Czech Republic in the first round in Paris and could face her old foe, Maria Sharapova, in the last 16.