World No. 3 Maria Sharapova will not compete in next week's U.S. Open due to right shoulder bursitis.

"Maria has informed us that she will be unable to compete at the US Open this year due to a right shoulder bursitis and has withdrawn from the tournament,” said US Open Tournament Director David Brewer.

Sharapova posted the following on her Facebook page:

"Hi everyone, I just wanted to let you know that withdrawing from the US Open has been a really tough decision to make. I have done everything I could since Wimbledon to get myself ready but it just wasn't enough time. I have done many tests, received several opinions and it all comes down to taking the proper amount of time to heal my shoulder injury properly. It's certainly not an easy decision to make ahead of one of my favorite tournaments, but I know it's the right one that will get me back on the courts soon. I plan on taking the next few weeks off, receiving proper treatment and rehabilitation. I will miss being part of the US Open, but can't wait for next year!"

Sources say that after her second-round loss to Michelle Larcher de Brito at Wimbledon, Sharapova went back to her home in Los Angeles and had a series of shots to treat pain in her surgically repaired shoulder. At least one of them was said to be a cortisone shot; the others may have been PRP (platelet rich plasma), which is said to use a portion of the patient's own blood to promote healing of injured tendons.

Sources also say that Sharapova has been suffering from shoulder trouble since June, and in her first two weeks of practice with now ex-coach Jimmy Connors, her shoulder hurt to the degree that she was unable to practice her serve at all.

The 26-year-old pulled out of Stanford and Toronto and was said to be advised not to play Cincinnati, but did anyway and lost her opening match to Sloane Stephens. She then traveled to New York and was training again with her father Yuri. On Wednesday, photos showed her attempting to serve, but apparently the pain was too great to think she could compete at the U.S. Open, where she last won the title in 2006.

Some members of Sharapova's camp think it could take her another two to three months to fully heal, which puts her at risk for the upcoming Asian swing and the WTA Championships. Sharapova underwent shoulder surgery in October 2008 and was unable to return to singles play until May 2009.

U.S. Open Tournament Referee Brian Earley said Agnieszka Radwanska will become the No. 3 seed and Anastasia Pavlyuchenkova will become the No. 32 seed.