After failing to continue a doubles match in Wimbledon because of a "viral illness," five-time Wimbledon champion Serena Williams is preparing for a comeback at the Bank of the West Classics in Stanford, U.S.

Serena was playing with her sister Venus at Wimbledon last July 1 when she lost balance, double-faulting four times while serving during the game. She barely knew how sick she was until much later when she rested.

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"I didn't realize how sick I was," said Williams.

Speculations were rife back then that Serena was down after her single's loss against 25th-seed Alize Cornet in the third round.

"I was really ill," responded Williams.

Normally, once a player had been eliminated in a game, the player would go home, but in Serena's case, she stayed in her room three days before leaving.

After the much-needed rest, Serena went off to Europe for a working vacation and a movie shoot. She even went to Croatia, as suggested by long-time hitting partner Sascha Bajin.

"Going to Croatia was unexpected. I'm glad I went," said 32-year-old Williams.

On Monday, Williams posted an Instagram picture of herself showing off her killer six-pack and amazing figure to show how determine she is in her return to the court.

Williams is scheduled to play in the second round against Czech Republic's Karolina Pliskova, who beat Kimiko Date-Krumm of Japan, 6-1, 6-3 Monday.

Third-seed German Angelique Kerber got to see Williams practice and said that she didn't see anything wrong with her. "She is back, for sure," said Kerber.

The World No. 1 Williams will use this tournament in preparation for her title defense at the U.S. Open slated this August in New York.

TagsVenus Williams, Alize Cornet, Sascha Bajin, tennis, Karolina Pliskova, Angelique Kerber