Serana Williams is out for the rest of the season.

In a statement e-mailed to the AP by her agent, the younger Williams said on Tuesday she "re-tore the tendon" in her right foot, which she originally injured by cutting it on glass at a restaurant shortly after winning Wimbledon in July. Williams had surgery in New York on Monday; she first had the foot repaired on July 15.

Her announcement comes less than two weeks after Venus Williams said she won't play for the rest of the year because of a lingering injury to her left knee. Both sisters will miss the WTA Championships next week in Doha, Qatar, and the Fed Cup final between the United States and Italy next month at San Diego.

Serena hasn't played on tour since July 3, when she overwhelmed Vera Zvonareva 6-3, 6-2 to win her fourth Wimbledon championship and 13th Grand Slam singles title overall, the most among active women.

The American cut her right foot on glass at a restaurant while she was in Munich, but she went ahead and played in an exhibition match on July 8 in Brussels against Kim Clijsters that drew a tennis-record crowd of more than 35,000. A week later, Serena had an operation on the foot in Los Angeles.

After withdrawing from the US Open, she returned to practice in September, but then put off her comeback by pulling out of tournaments in Tokyo, Beijing and Linz, Austria.

On October 10, in a posting on her official website, Serena said she "re-strained" her foot by overtraining and "likely" would be out for the year.

Her statement on Tuesday said: "It is with deep frustration that I am withdrawing from the WTA Championships at Doha and the Fed Cup Final. Pushed by my desire to return to competition, I trained too hard too soon and re-tore the tendon in my foot. As a result, yesterday morning I had to have another procedure to repair it. I thank everyone for their continued support."

Serena lost the No. 1 ranking last week to Denmark's Caroline Wozniacki, who has yet to win a Grand Slam.