LONDON (Reuters) – Kim Clijsters will find it hard to compete at the top level when the WTA Tour resumes following the coronavirus pandemic, says old rival and fellow former world number one Ana Ivanovic.

Belgian mother-of-three Clijsters surprised the tennis world when she announced she was making a second comeback this year.

The 36-year-old four-time Grand Slam champion failed to win a match in the two tournaments she played before the coronavirus pandemic forced the suspension of the season — losing to Garbine Muguruza in Dubai and Johanna Konta in Monterrey.

“I have been watching some of her matches and she has been striking the ball amazingly well, but I really hope she can get back to that level to play like she used to,” Serbia’s 2008 French Open champion Ivanovic, talking to Eurosport’s Hanging out with Babsi, said on Wednesday.

“Personally, I don’t think it’ll be easy after being out for so many years.”

Clijsters first retired in 2007, taking a break to have the first of her three children, but returned within 24 months to claim three of her four Grand Slams and return to world number one in 2011. Her latest comeback could prove more challenging.

“It’s amazing what she achieved. I still respect her so much, it’s just difficult to imagine now after having three kids and being out for so long to make a comeback,” Ivanovic, who retired in 2016, aged 29, said.

“Not because she’s not fit, but because your body just reacts differently. When you are out of competition you realise how much fine-tuning is necessary and she’s been out a while.”

With the WTA Tour on hold until at least the start of August, Ivanovic said the long stoppage could hinder the likes of older players such as 38-year-old Serena Williams, who remains one shy of equalling Margaret Court’s record of 24 Grand Slam singles titles.

“Some players find it easier to get used to. Some players get injured for a few months, come back and they are as strong as before,” she said. “It is very individual but you would think it would favour the younger players because it would be easier to get match fit and into match rhythm.”