Tennis: Nadal retires injured from US Open semi-final

Rafael Nadal is out of the US Open retiring against Juan Martin del Potro. The Spaniard was trailing 7-6 (7-3) 6-2 when he quit the match because of injury. Nadal was emotional upon leaving the court as his title defence came to an end. Del Potro, 2009 champion, will face either Novak Djokovic or Kei Nishikori in the final.