© 2012 Daily Tennis News Wire -
Rafael Nadal faces a threat to his Miami Masters campaign after admitting he's suffering with left knee problems after edging past Jo-Wilfried Tsonga to reach the Miami Masters semi-final and set up a showdown with Andy Murray.

"I have problems on my left knee, that's the thing.  I'm not feeling great," said the three-time finalist. "I don't know what's gonna happen in the next match, because gonna be a big match against one of the toughest opponents on tour. Probably I don't arrive in my perfect conditions to that match.

But Nadal also added that besides the knee, he's on his game. "I'm feeling great, I'm not tired today now after three hours' match.  My fitness is perfect, it's not a problem. "The negative thing is I have to recover well.  I have to improve my knee if I really want to have any chance to win. If not, it's gonna be almost impossible. 

"But it's always is fantastic being in semi-finals, at the first two Masters 1000s of the year. Being in both semi-finals on hard court are fantastic results."

Nadal took all of February away from tennis to rest and recover and is only playing his second tournament since returning. He suffered a semi-final thrashing by Roger Federer this month at Indian Wells.