Knee trouble forces Nadal out of Miami

Rafael Nadal withdrew from the Miami Masters prior to his scheduled semi-final against Andy Murray on Friday with a knee injury. \"So sorry for my fans, those here at Miami and those around the world,\" the Spanish world number two wrote on his Twitter account. \"My knee won\'t let me play today.\" It\'s a blow for Nadal with the start of the clay court season looming. Nadal is playing in only his fourth tournament of 2012 having fallen in the semi-finals in Doha, finished runner-up to Novak Djokovic in January\'s Australian Open final and making the Indian Wells Masters semi-finals last week. His last title came at the French Open last year. \"Rafael Nadal has been forced to withdraw from today\'s match at the SEOpen due to a knee injury,\" a posting on the ATP\'s Twitter feed said. \"Andy Murray advances to the final.\" Murray, who won the Miami title in 2009, awaits the winner of the semi-final between world number one Djokovic and Juan Monaco of Argentina, the 21st seed who ousted Andy Roddick and eighth-seeded Mardy Fish en route to the semis. \"We are disappointed that Rafa has been forced to withdraw from the tournament but the health of the players always needs to be the number one priority,\" said Adam Barrett, Sony Ericsson Open Tournament Director. \"He has played some great tennis and is a tremendous ambassador for the game. We wish him a speedy recovery and hope to see him back on the court soon.\"