Rafael Nadal will have to wait still another year for a title at the Sony Ericsson Open.

The second-seeded Spaniard was forced to withdraw from Friday's scheduled semifinal against Andy Murray because of a knee injury. He was coming off a three-set victory against Jo-Wilfried Tsonga in the quarterfinals on Wednesday night.

"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."

Nadal has never won the Masters event in Miami, finishing as the runner-up on three different occasions. He was beaten by Novak Djokovic in last year's finale, fell to Nikolay Davydenko in 2008 and lost to Roger Federer in 2005.

Murray, the 2009 Miami champion, will advance to Sunday's final with the walkover and will face the winner of Friday's second semifinal between Djokovic and Juan Monaco.