Azarenka and Sharapova both in doubt for start of U.S. Open
August 10, 2012 -- Updated 2126 GMT (0526 HKT)
Top-ranked Victoria Azarenka is a big doubt for the U.S. Open, which starts on August 27.
- Victoria Azarenka is struggling for full fitness after heavy schedule this season
- Australian Open champion will also miss next week's Cincinnati Masters
- Belarus star is hoping to make it past fourth round at Flushing Meadows for first time
- Second-ranked Maria Sharapova withdraws from second consecutive event due to illness
(CNN) -- World No. 1 Victoria Azarenka is facing a race against time to be fit for the U.S. Open after succumbing to the frenetic schedule of women's tennis.
The Belorussian was forced to withdraw from the Montreal Cup with an injury to her left knee midway through the first set of her opening match against Tamira Paszek on Thursday.
With just 17 days until the start of the competition at Flushing Meadows, the Australian Open champion's hopes of adding to her sole grand slam triumph look slim.
The 23-year-old reached the semifinals of Wimbledon last month, before going on to compete at the London 2012 Olympics where she won bronze in the singles and gold in the mixed doubles on Sunday.
The workload has taken its toll on Azarenka, who will now also miss next week's Cincinnati Masters event.
Victoria Azarenka targets 2012 success
World No. 4 Maria Sharapova has long been known for her on-court shrieks and the Russian has recently attracted criticism as a result. The three-time grand slam champion claimed she will continue to make the noises until they are outlawed.
The noisiest players in tennis
World No. 1 Victoria Azarenka has come a long way since first picking up a tennis racket in her native Belarus.
The tennis journey of Victoria Azarenka
Sharapova: It's a special victory
"The last week took so much energy out of me that I had absolutely no time to recover, and my body is feeling it," she told reporters.
"It was a little bit too quick of a transition for me to come and start the training, and I felt my knee just wasn't in good shape.
"It's unfortunate because I was really looking forward to playing here. I have really enjoyed being here. I tried yesterday and today it just got worse. I can't see the point of continuing to play if I can't give even 50% of my game."
Azarenka, who has never made it past the fourth round at the U.S. Open, said she needs rest and recuperation if she is to line up in New York later this month.
"I hope it's a short-term thing. I have to just stop and take a little bit of time off because I had absolutely no rest for a long period of time. I just need to settle it down and go from there. Hopefully there's nothing serious about it," she said.
"If I cannot play here, there is no chance for me to play anywhere else. My first goal is to get healthy and make sure I'm 100% ready to play the U.S. Open."
The hectic schedule claimed another victim when world No. 2 Maria Sharapova also pulled out of the WTA Tour event in Cincinnati.
The French Open champion, who was defeated in the Olympic final by Serena Williams, missed Montreal due to a stomach virus.
The Russian hopes to recover in time for the U.S. Open, which she won in 2006.
Part of complete coverage on
September 11, 2014 -- Updated 1248 GMT (2048 HKT)
His distinctive crocodile logo is seen on clothing all over the world, but Rene Lacoste also left a lasting legacy in the development of tennis.
September 9, 2014 -- Updated 0636 GMT (1436 HKT)
Marin Cilic follows in the footsteps of his coach Goran Ivanicevic by claiming a grand slam crown for Croatia, winning the U.S. Open.
September 14, 2014 -- Updated 1334 GMT (2134 HKT)
Serena Williams is without peer in the modern women's game and now she is on a par with two American tennis legends from the past.
September 2, 2014 -- Updated 1321 GMT (2121 HKT)
Over the course of her remarkable life, Althea Gibson was many things to many people -- but it was tennis where she really left her mark.
August 27, 2014 -- Updated 1145 GMT (1945 HKT)
Canada and tennis? Really? Yup. The North American tennis power balance is swinging away from the States.
August 21, 2014 -- Updated 1252 GMT (2052 HKT)
As a player he was as fiery as his hair -- and as Novak Djokovic's coach, Boris Becker says he has to battle to keep his emotions in check.
August 20, 2014 -- Updated 1102 GMT (1902 HKT)
Tennis great Boris Becker says he was stunned by the level of criticism he received after being appointed as Novak Djokovic's coach.
July 25, 2014 -- Updated 1101 GMT (1901 HKT)
"I didn't cry once when I practiced in front of the mirror," says Martin Emmrich. But the nerves kicked in when he got down on one knee on court.
June 30, 2014 -- Updated 1135 GMT (1935 HKT)
When Agnieszka Radwanska refused to look her opponent in the eye after losing at Wimbledon, it raised more than eyebrows.
June 23, 2014 -- Updated 0114 GMT (0914 HKT)
It's 10 years since a teenage Maria Sharapova became the darling of Wimbledon's hallowed Center Court, launching herself as a star.
May 23, 2014 -- Updated 0746 GMT (1546 HKT)
He's regularly voted France's favorite famous person, but many of the nation's youth have "no idea" about his glorious sporting past
April 29, 2014 -- Updated 1555 GMT (2355 HKT)
Five-time grand slam champion Martina Hingis has followed her mom into a coaching role, setting up a new tennis academy in Barcelona, Spain.
Today's five most popular stories