St. Petersburg, FL (SportsNetwork.com) - Former world No. 1 Maria Sharapova is done playing tennis for 2013.

The world No. 3 Russian star withdrew from the upcoming season-ending WTA Championships because of a right shoulder injury, which also forced her to skip the U.S. Open.

Sharapova was the Championships runner-up in Istanbul last year.

"I am very disappointed that I will not be able to play in the TEB BNP Paribas WTA Championships this year," Sharapova said. "The fans in Istanbul have welcomed us each year with such intense passion and warmth, I will sincerely miss the energy and excitement they brought to the year-end tournament. I want to thank Istanbul for being a tremendous host and hope to play in Turkey sometime in the future."

This is the last year Istanbul will host the tournament, as The Championships shift to Singapore next year.

This season, Sharapova captured titles in Indian Wells and Stuttgart, and was a runner-up in Miami, Madrid and at the French Open, losing each time to current No. 1 Serena Williams.

After bowing out of Wimbledon in the second round, Sharapova cut ties with her long-time coach Thomas Hogstedt and then had a brief partnership with the legendary Jimmy Connors, which lasted for one match.