STAMFORD, June 11: Steffi Graff said it was unlikely she would play any further Grand Slam tournaments this year after undergoing knee surgery in Vienna.

The former world number one and 21 times Grand Slam champion had a two-hour operation on her left knee at an undisclosed hospital in the Austrian capital. Doctors expect she will not be able to compete for another four to six months.

``I am deeply disappointed that I will be able unable to defend my Wimbledon title this year,'' Graf said yesterday in a statement issued from the headquarters of the Women's Tennis Association (WTA).

``When exactly I will be able to compete again is not clear. The doctors told me that with extensive physiotherapy, returning in four to six months is realistic.

``It seems unlikely that I will be able to defend my US Open title as well.''Graf, who was knocked out of the French Open by Amanda Coetzer in the quarter-finals last week, was reportedly recovering in a private clinic.The seven times Wimbledon champion said the injury was identified during magnetic resonance imaging (MRI) last Friday which showed a cartilage fracture and partial rupture of a tendon.

``I have been assured that the surgery went very well and I feel fine right now,'' said Graf.

The German said she first suffered the injury at Wimbledon last year.Graf, 27, said she had arthroscopic surgery after defaulting from a tournament in Tokyo in February in a bid to be ready for the French Open and Wimbledon.

``The actions I have taken today tackled the problem at the root and I am confident that I will be able to return to the game I love so much this time healthy,'' she said.

Graf said she experienced pain during last week's French Open.

She was also hampered by an infected toe at the Australian Open in January when she fell in the fourth round, again to Coetzer.

Graf, the defending Wimbledon champion, slipped to number three in the world rankings following her shock loss in Paris.

Wimbledon starts on June 23 and the US Open begins on August 25.

Copyright © 1997 Indian Express Newspapers (Bombay) Ltd.