Rafael Nadal zipped around Court Philippe Chatrier as though he had rockets in his heels on Wednesday during a straight sets quarter-final win over Nicolas Almagro but he was still not quick enough for the umpire.

Nadal rarely gets flustered during matches but lost his rag with chair umpire Stefan Fransson at the end of the ninth game after getting a second warning over the time he was taking in between points.

Considering he was wearing a sponsor's watch worth half a million dollars he really did not have a leg to stand on and Nadal was charm personified when he explained the incident.

"If I deserve it, I deserve it," four-times champion Nadal told reporters after being fully extended for the first time in the tournament by aggressive 19th seed Almagro in a 7-6, 7-6, 6-4 victory.

"I think this put a bit of pressure on me, then I had to play with pressure.

"But these are the rules, and I understand the rules. They told me already I was a bit slow and taking a bit too much time," he added 

Nadal, who turns 24 on Thursday, felt the second warning was harsh, especially as it came at crucial phase of the match when fellow Spaniard Almagro earned a break point at 4-4 which Nadal fended off with superb serve and volley play.

"I thought I was being very fast. I didn't even take the time to wipe my face," he said.

"I didn't want to be fined or to get a penalty point. I was making big efforts to be as quick as possible.

"I think the second warning was not a warning I deserved," added Nadal in his most endearing Spanglish.

His time-keeping was a bit off but there was not much wrong with his game once he recovered from losing the opening three games against a dangerous opponent.

"I started terrible," said Nadal, who faces unfancied Austrian Jurgen Melzer in the semi-finals and could meet Sweden's Robin Soderling, the only man to beat him at Roland Garros, in the final.

"I started the beginning of the match terrible. I threw all the balls outside. I came back very soon to 3-3 so that was very important for me in the first set.

"I'm very happy how I played the tie-breaks. I played aggressive, very focused, and in the important moments I think I played better than the rest of the match," he added.

Austrian Jurgen Melzer produced a dramatic fightback from two sets down to send third seed Novak Djokovic spinning out of the French Open on Wednesday.

Melzer, playing in the quarter-finals of a Grand Slam for the first time, looked down and out before an incredible revival earned him a 3-6, 2-6, 6-2, 7-6, 6-4 victory.

Novak Djokovic blamed a close line call for his shock five-set defeat by Austrian Jurgen Melzer.

The Serbian third seed was cruising after pocketing the first two sets with razor-sharp tennis but the wheels fell off when he led 2-0 in the third and he slumped to a demoralising defeat in more than four hours.

When 22nd-seed Melzer served for the match at 5-4 in the fifth he fluffed a forehand and appeared to have been wrong-footed by a Djokovic crosscourt as he approached the net.

The ball appeared to have touched the line but when Melzer asked the umpire to climb off his chair and inspect the mark, Carlos Bernardes deemed that it had landed out meaning that instead of being down 0-30 the Austrian was back at 15-15.

Djokovic could not believe his eyes and was still chuntering about the decision after the match, although he only had himself to blame for wasting the chance to face Rafael Nadal in the semi-finals.

"From my side and from my perspective, it was looking good," the 23-year-old former Australian Open champion told reporters.

"There was no space between the line and the mark, and that means the ball is good.

"I don't know why the chair umpire got that decision wrong. And there was another ball on 4-4, my advantage, as well, and the ball was out. But this is all part of the sport," he added.