Serena Williams pulled out of her last two scheduled tournaments of the season Friday in hopes of being healthy for 2006.
Williams, who won the Australian Open this year for her seventh Grand Slam title, will miss the event in Zurich, Switzerland, next week, and the Philadelphia tournament that begins Oct. 31.
She's been hampered by left ankle and knee problems for months and played only 28 matches in 2005, going 21-7.
Williams skipped the French Open, was upset in the third round at Wimbledon, and lost to older sister Venus in the fourth round of the U.S. Open. She then lost her opener at the China Open to 127th-ranked Sun Tiantian in straight sets on Sept. 21, and hasn't played since.
"My doctors and trainers have advised me that my leg needs to fully recover in order for me to play at the level that I'm accustomed to playing," Williams said in a statement released by the WTA Tour.
"This has been such a disappointing year for me because I'm such a competitive person and I like to win for myself and for my fans. I tried my best to fight through my injuries during the season, but I now realize that I need to take some time off to rest my body and get back to being 100 percent healthy."
Once No. 1, she has slipped to 11th in the WTA Tour rankings.
"I'm going to be busy these next several weeks rehabbing, training and getting healthy so that I can play my very best for myself, the fans, tournaments and sponsors in 2006," Williams said, AP reported.