Maria Sharapova pauses during play against Serena Williams during their...

Maria Sharapova pauses during play against Serena Williams during their women's singles semifinal match at the All England Lawn Tennis Championships in Wimbledon, London on Thursday, July 9, 2015. Credit: AP / Pavel Golovkin

Maria Sharapova's Grand Slam season has come to an end. She announced Sunday that she has withdrawn from the U.S. Open, citing the leg injury that has kept her out of competition since Wimbledon.

The 2006 U.S. Open champion lost to Serena Williams in the Wimbledon semifinals, then took the rest of the summer off to recuperate. At a news conference Saturday, she did not indicate that the leg injury still is a problem, but she also was less than enthusiastic as she answered questions.

Injuries have significantly impacted her career, particularly problems with her right shoulder that necessitated surgery.

"It's always just the adjustments of being a professional athlete in a sport that requires many weeks out of the year to compete at a high level, and you sometimes don't know where things come from, but you have to make the adjustments to be healthy and ready for the big ones," Sharapova said Saturday. "I have had to over the years and it only gets tougher as you get older."

She described the injury as a bit of a muscle strain and said she had gone through the gamut of therapies.

The 28-year-old was the No. 3 seed and highest-ranked player that No. 1 Serena Williams could have faced before the Open final as she tries for the calendar year Grand Slam. Williams holds an 18-2 match advantage over Sharapova.

Her spot in the draw will be taken by "lucky loser" qualifier Daria Kasatkina. That means the first-round match at Armstrong Stadium that Sharapova was scheduled to play will be a battle of the Darias. Sharapova would have faced Daria Gavrilova, who had beaten her once this season.

"I have done everything possible to be ready but it was just not enough time," Sharapova said in a Facebook post Sunday, vowing to finish the year "healthy and strong."

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