World number eight Milos Raonic has withdrawn from the ATP World Tour Finals because of a quad injury.
The Canadian was due to face Kei Nishikori at London's O2 Arena this afternoon, although first alternative David Ferrer has now been drafted in.
"You, the fans deserve a great show and I wouldn't step out if I couldn't," Raonic tweeted. "I am sorry for the fans. I will do everything to be here next year."
It means that should Andy Murray lose his Group B match against Roger Federer this evening, he will be eliminated from the end-of-season competition.
