World number one Serena Williams will not play again on the WTA Tour this year in order to ensure she is fully fit for next season.

Williams missed out on securing a first calendar Grand Slam when she suffered a sensational defeat to Roberta Vinci in the semi-finals of the US Open last month.

The 21-time grand-slam champion on Thursday revealed that she will miss the China Open, which starts on Saturday, and the WTA Finals in Singapore for the good of her health.

Williams said in a statement published on the China Open website: "It's no secret I've played injured most of the year - whether it was my elbow, my knee, or, in the finals moments after a certain match in Flushing (Meadows, following her defeat to Vinci), my heart.

"I'm a fierce competitor. And I want to compete as well as I can, for as long as I can. So I am taking a proactive step and withdrawing from tournaments in Beijing and Singapore to properly address my health and take the time to heal.

"This is a very difficult decision, but one ultimately made because of the love of the game. I plan to return to practicing and participating in exhibition matches later this year. And when I do, l will focus and focus and focus so I can continue my journey in this beautiful game."

Williams reflected on an incredible year in which she completed a second 'Serena Slam' - holding all four majors at the same time - with pride after cutting short her season.

"Arthur Ashe once said, 'Success is a journey, not a destination'. The doing is often more important than the outcome. My journey in tennis this year has been at times exhilarating, at times disappointing, but in every case, in victory and defeat, it has been extremely rewarding," she added.

"I've grown more this year than perhaps at any other point in my career. The tennis family, and our fans, have embraced and supported me in ways I never imagined. I am grateful beyond words.

"I love this game more than ever. I hold deep respect for all those who have graced our courts. I've been privileged to be one of the few to understand their struggles and their triumphs."