World number-three men's tennis player Andy Roddick of the United States has pulled out of the Tennis Masters Cup which gets under way Sunday in Shanghai.
Roddick, who suffered a lower back injury in his quarterfinal match at the Paris Masters last week, will be replaced in the eight-man draw by David Nalbandian of Argentina.
The 23-year-old American said he had tried to continue practicing, but muscle spasms in his lower back have persisted. Doctors have told Roddick that he must stay off the court for the next 10-14 days.
This was Roddick's third straight year qualifying for the season-ending Tennis Masters Cup. He advanced to the semifinals in 2003 and 2004.