Serena Williams is expected to hit the tennis court soon as she prepares to defend her US Open crown. Still, many wondered what happened to the American tennis star during his rough spell at Wimbledon few weeks ago.

In an interview with France's Tennis Magazine, Serena's coach and rumored boyfriend Patrick Mouratoglou downplayed rumors that his relationship with the multiple Grand Slam winner is getting sore, though he admitted that Williams had undergone through difficult moments as of late.

"Serena is clearly going through a difficult period. But since Wimbledon, we have had long hours of talks and we are getting back to work," Mouratoglou said in an interview with the publication.

"Today she is in the mood to get back to training so she can return even stronger. At no time was there any question of us stopping our collaboration."

Mouratoglou, who has been romantically linked to Williams these past two seasons, did not deny or confirm if Serena's problem was something of personal matters. However, he clearly knows that Williams had some bad moments.

"I have never discussed private matters and I am not going to talk about them now. There have been difficult things. For sure, Serena is in a difficult phase but I will leave it there," the coach added.

The 32-year old Williams experienced health scare two weeks ago when she surprisingly bombed out of Wimbledon Open championships in both women's singles and doubles competition.

Williams lost to Alizé Cornet of France in the third round and had a bizarre moment when she and her sister decided to retire from their doubles match against Kristina Barrois of Germany and Stefanie Vögele of Switzerland.

Serena was clearly fatigued during the match as she couldn't even serve the ball into the opponents' court. She blamed a stomach virus for her lackluster effort, but several tennis pundits - including tennis legend Maria Navratilova - were a bit suspicious of her health condition.

"I find it distressing," Navratilova told USA Today. "I think a virus, whatever they're saying it was, I don't think that was it. I think it's clear that's not the case. I don't know what it is, but I hope Serena will be OK."

There are rumors about Williams' alleged pregnancy, but she downplayed such speculation without saying a single word by flaunting her curves during her latest Croatian vacation. Williams also tweeted her coach that she's excited to get back into action in time for the US Open championship, which starts late August.

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