Serena Williams announced she would be unable to play the BNP Paribas WTA Finals Singapore due to a shoulder injury. 
The 35-year-old 22-time Grand Slam champion made the announcement late on Sunday after missing all of the Asian Swing due to that same issue; shoulder problems also kept her out of the Rogers Cup and Western & Southern Open earlier in the summer. 
Williams has participated in eight tournaments this season, winning two titles at the Internazionali BNL d'Italia and Wimbledon, where she tied Stefanie Graf for the Open Era record of Grand Slam titles. 
Serena Williams also reached the finals of the Australian Open and French Open, and tied Graf for the all-time record of most consecutive weeks at World No.1, at 186 straight weeks.

Source: QNA