Roger Federer had the luxury of watching from the locker room and must have liked what he saw. Rafael Nadal duly won his semi-final against Rainer Schüttler in straight sets here yesterday to earn a place in the final against Federer for the third year in succession, but this was the Spaniard's least impressive performance of the tournament.

Having demolished Mikhail Youzhny and Andy Murray, Nos 17 and 11 in the world respectively, in the previous two rounds, Nadal struggled to see off Schüttler, the world No 94, before winning 6-1, 7-6, 6-4 in just over two hours.

Nadal's movement has been one of the most significant improvements in his grass-court game this year, but on this occasion, playing in different shoes, he never looked sure of his footwork. After dominating the first set, in which he made only one unforced error, the French Open champion made 17 in the last two.

It was not the sort of form Nadal wanted to show as he prepared for his date with history. The world No 2 is attempting to become only the third man in the Open era to win the Roland Garros-Wimbledon double in the same year, after Bjorn Borg and Rod Laver. He would also be the first Spaniard to win at the All England Club since Manuel Santana in 1966.

"Maybe today wasn't my best match here this year," said Nadal. "The first set was very easy, which is always a good thing, but at the same time it's difficult when your opponent then starts to play better. That can make you feel strange on court. But the most important thing is that I'm in the final."

Schüttler, playing less than 24 hours after completing his five-hour quarter-final against Arnaud Clément, was the most unlikely of semi-finalists. The 32-year-old German is a former world No 5, but his ranking had fallen so far that he was playing tournaments on the Challenger circuit earlier this year.

If his victories here had restored his confidence there was no evidence of it in the first set, which was over in 23 minutes. Schüttler was broken to 15 in his first two service games, went 0-4 down and lost the set when he put a limp forehand in the net.

As Schüttler went 2-0 down in the second set he screamed in frustration, imploring himself to be more aggressive. It did the trick as Nadal dropped his serve for only the fourth time in the tournament.

Thereafter the Spaniard made a steady flow of mistakes and would have lost the set had Schüttler not weakened when serving at 5-4. At 15-30 the German let out another scream after a careless forehand, only to repeat the mistake on the following point. The set went to a tie-break, which Nadal won 7-3.

Schüttler was broken in the third game of the final set. Serving at 3-5 and 0-40 he made a final gesture of defiance, winning five points in a row, but Nadal duly served out for the match.

While Nadal's performance was patchy, there was still some evidence of the improvements he has made to his game this summer. He won 12 of the 14 points he played at the net, played aggressively when he could, hitting 40 winners to Schüttler's 21, and served impressively.

Always modest and respectful towards Federer, Nadal was asked if he knew how to beat the world No 1 on grass. "No," he replied to the amusement of the post-match press conference. "I can only try my best, try to find my rhythm and my intensity. If he plays better than me and beats me I'll just congratulate him like I do every year."