djokovic knocks murray out of us open
Andy Murray is out of the US Open after a brutal quarter-final against Novak Djokovic. The world number one took the game three sets to one. Murray looked to be struggling with a back injury for the final set. Djokovic will now play Kei Nishikori in the semi-finals. Serena Williams booked her place in the last four with a straight sets win against Flavia Pennetta.
