Nadal can dash the dreams of Djokovic and Federer PARIS (Reuters) - Novak Djokovic is getting jittery thinking about the "Novak Slam" while Roger Federer is fantasizing about "number 17." Chances are, though, that both aspirations will be smashed into smithereens of red dust by a French Open dream-wrecker called Rafa Nadal. No-one could accuse Djokovic of being boring or lacking heart as he clung on by his fingertips to his Roland Garros hopes to set up a lip-smacking semi-final with 16-times grand-slam champion Federer. Four times Djokovic came within one false step of losing out on the chance of holding all four majors at once as Jo-Wilfried Tsonga held match points in their heart-thumping quarter-final. Four times Djokovic dodged the bullet that would have blown apart his dreams. In case the Serbian thought the stars were now lining up for him to complete a feat no man has done in 43 years, John McEnroe was quick to give him a reality check. "If it hasn't been done in 43 years, you get the idea it's tough," the seven-times grand slam champion told reporters on Thursday. It is an achievement that eluded greats such as Pete Sampras, Andre Agassi, Bjorn Borg, Jimmy Connors and even Federer and Nadal. In fact Federer came within three sets of completing the four in a row at the French Open in 2006 and 2007 - only to find Nadal blocking his path to glory in the finals. Just as Federer found Nadal an insurmountable hurdle, McEnroe cannot see anyone denying the man from Mallorca, who faces fellow Spaniard David Ferrer in the other semi-final, a record seventh Paris crown. Nadal has dropped only 30 games to his first five opponents, while in their last two matches alone, Federer has lost 36 games and Djokovic 46. "It's going to be unbelievably tough to beat this guy," McEnroe said. Novak I think is really feeling the pressure like he did last year. It's impossible not to feel that because he's so close. I guess Roger was this close. He had won three in a row and was in the finals (here) twice. Rafa was in the same position in Australia (in 2011). There's obviously nothing better than the chance of doing something that hasn't been done for 43 years ‑ having four majors in a row. So that alone makes it almost impossible to play as well as you can. The pressure alone, and the expectation to have to be able to do that and execute it, is almost impossible. Djokovic has certainly been feeling the heat this week, surviving back-to-back five setters, and life is unlikely to get much easier on Friday. He will be facing off with the man who ended his 43-match winning streak at the same stage a year ago, the last time the world number one was beaten at a slam. With their rivalry heading into a 26th showdown, and Federer leading 14-11, there will be an air of familiarity between the players and the one thing they are both prepared for is a long, drawn-out battle. As for the other semi-final, Nadal has so far hurtled through the draw with a 15-0 sets record and even though Ferrer, who has dropped just one set, is playing the best tennis of his career, McEnroe did not rate his chances. "He's a middleweight playing against heavyweights," summed up the American.