Andy Murray will need to come through "one of the best challenges in tennis" today if he is to reach a first French Open final.
The world No 4 takes on world No 1 Rafael Nadal, who is bidding to equal Bjorn Borg's record of six titles at Roland Garros -- a venue where he has only ever lost one match.
Both have had eventful paths through to the last four, with Murray hurting his right ankle then almost crashing out to Viktor Troicki; Nadal was two sets to one down in his first-round match against John Isner.
The Scot, who has never made a secret of how much he likes and admires Nadal, said: "It's one of the best challenges in tennis. His record here is incredible. I'm looking forward to it but I know it's going to be an incredibly difficult match for me."
Nadal has looked as vulnerable as he ever has at Roland Garros and, far from playing down his struggles, the Spaniard has been keen to describe in detail his mental and physical problems. However, he looked back to his old self in his quarter-final win over Robin Soderling -- the only man to have beaten him here.
The Spaniard, who turns 25 today, said: "Playing against Andy is always a big challenge because he has all the shots. He can defend very well, he can attack very well and he runs fantastic.
"The only way that you can beat him is playing at a very, very high level."
The other semi-final between Roger Federer and Novak Djokovic is the most eagerly-awaited match at Roland Garros this year and, for Djokovic, it could be a life-changing one.
Victory over the 16-time Grand Slam champion would see the Serb overtake Nadal to become world No 1 for the first time, and he would also equal John McEnroe's 1984 record of 42 straight wins to start a season.
Were Federer to win, the Swiss would reach the final for the fifth time in six years and show that he is not ready to make way for the Nadal and Djokovic show just yet.
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