Serena Williams appeared to be in pain during her last three matches at the China Open and had to take a medical timeout after complaining about back pains, leaving many fans wondering if her coach and rumored boyfriend Patrick Mouratoglou is wearing her out with all of the tournaments he is making her participate in.

"I've been a little tight all week. It's been a long year, so I was really happy," Serena Williams mentioned during a public interview following the final of the China Open.

Serena Williams has never used the on-court coaching rule which has been implemented on the tennis court for the last couple of years, TennisWorldUSA.org reports.

Her coach and rumored boyfriend Patrick Mouratoglou is usually in the stands to watch her matches but does not come down to the court for coaching in-between sets, TennisWorldUSA.org also reports.

Serena Williams has captured the attention of fans throughout her performance at the China Open, but many fans are also wondering if she's still dating her coach and rumored boyfriend Patrick Mouratoglou - she hasn't shown any public display of affection since the US Open.

While her coach has supported her on his Twitter page with messages that point to her success within the tournament, Serena Williams hasn't stopped to show any affection for Patrick Mouratoglou.

Shortly after the U.S. Open, Serena Williams denied rumors surrounding her relationship with her coach saying "You just do not mix pleasure with business, I firmly believe in not mixing pleasure with business."

A hockey player named Dan Ogee posted a photo of a trophy he appears to have won and tagged the US Open star in his post, saying "my trophy is bigger than yours."

Serena Williams responded, saying "Wow can I have it?" and he answered back, saying "Nope, but you can drink from it."

Perhaps the Twitter back-and-fourth exchange might have made Serena Williams' coach and rumored boyfriend Patrick Mouratoglou jealous?

Serena Williams has spoken about all about her personal and social life on Twitter, except for her coach and rumored boyfriend Patrick Mouratoglou.

Serena Williams and her coach Patrick Mouratoglou have long been rumored to be dating, but one website suggests the couple might not have ever dated.

"The pair have never openly admitted to being anything more than player and coach, but the media and especially the tennis writing press have largely ignored this fact and assumed that they are a couple, to the point that there are now rumors about the so-called 'couple' having split up," SteveGTennis.com reports.