Serena Williams has withdrawn from the Dubai Championships because of a lower back injury.

Agnieszka Radwanska extended the best winning streak of the year to 11 matches as she rolled into the third round of the Australian Open with a 6-3, 6-3 win over Romania's Irina-Camelia Begu on Wednesday.
People have been treating Andy Murray differently since he won his first major and ended that long drought for British men at tennis' Grand Slam tournaments.
Just when it looked as if he was headed for his offseason vacation, Novak Djokovic started playing his best tennis.
Andy Murray won his first match in Britain since winning his first Grand Slam title, beating Tomas Berdych 3-6, 6-3, 6-4 on Monday in the opening match of the ATP finals.
Serena Williams returns to the WTA Championships with the Wimbledon and U.S. Open titles, plus the Olympic gold medal, yet with no chance of finishing the year as the No. 1 in the world.
Venus Williams lifted the undefeated Washington Kastles to the World Team Tennis final Saturday, beating Ashley Harkleroad in the evening's last match to secure the Kastles' 19-15 victory over the New York Sportimes.
First came the victory in the Tour de France. Then there were the stacks of medals at a dazzling Olympics at home.
After reveling in a rousing Olympic summer of sporting success, Britain awoke Tuesday to another major milestone: Finally, after 76 years of waiting, the country has a male Grand Slam tennis champion.