Serena Williams holds her head after losing to Roberta Vinci of Italy during a semi-final match at the US Open tennis tournament.

BEIJING, AP:

The 2015 season is over for Serena Williams. The number one-ranked Williams withdrew from her final two scheduled tournaments of the year yesterday, saying she needs time to heal from a series of injuries and the heartbreak of coming up short in a bid for a calendar-year Grand Slam.

Williams hasn't played since losing to Roberta Vinci in the semi-finals of the US Open, where she came two matches short of becoming the first player to win all four majors in the same year since Steffi Graf in 1988.

"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, my heart," Williams said in a statement.

Williams pulled out of next week's China Open in Beijing and the season-ending WTA Finals to be held in Singapore from October 25-November 1.

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

In 2015, Williams won the Australian Open, the French Open and Wimbledon.

Williams said she plans to get back on the court during the off season and prepare for the Australian Open in January, where she will be going for her 22nd Grand Slam title. That would tie 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 said.

"I plan to return to practising 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."