Wuhan (China), Oct 2 (IANS): American tennis icon Serena Williams has called it a season, announcing her withdrawal from her last two scheduled stops of 2015 - the China Open and the WTA (Women's Tennis Association) Finals in Singapore.

The 21-time Grand Slam singles champion withdrew to address her health and to heal, Xinhua reported.

Serena has had one of the most successful seasons of her career this year, highlighted by winning three Grand Slam titles -- the Australian Open, French Open and Wimbledon -- to bring her career haul to 21, and already securing the WTA year-end world No. 1 ranking, her third straight year finishing on top of the WTA rankings, and her fifth year overall.

But all of the injuries she's had to overcome throughout the year finally caught up with her. The news was posted on the official website of the China Open, which will get underway this Saturday.

"It's no secret I've played injured most of the year -- whether it was my elbow, my knee, or, in the final moments after a certain match in Flushing Meadows, my heart," Williams said, referring to her semi-final loss to Roberta Vinci at the US Open, where she was two wins away from the calendar year Grand Slam.

"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."

The 34-year-old hopes to get back on the court during the off-season. At the Australian Open in January, she will be going for her 22nd Grand Slam title, which would tie German legend Steffi Graf for most in the Open Era.

"This is a very difficult decision, but one ultimately made because of the love of the game," Williams added. "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."

WTA president Micky Lawler said: "Serena's health has to be her number one priority. The risk of injury is a reality in the world of elite athletic performance. We will miss seeing Serena on court in Singapore and wish her a speedy recovery."

"We have a superb line-up of top players already qualified, and still in contention for qualification, at the WTA Finals Singapore, so fans can expect more outstanding, world class competition on the court again this year."