It was a breathless Wimbledon contest that kept on giving for almost five hours - diving volleys, ferocious forehands, blazing backhands and even acrobatic tumbles - and at the end of it all Rafael Nadal was the one left standing on Wednesday.

Juan Martin del Potro lay sprawled face down on the slippery and dusty Centre Court turf as Nadal punched away a final backhand volley to seal a 7-5 6-7(7) 4-6 6-4 6-4 win that took him into the semi-finals for the first time since 2011.

"It was a very emotional match... great quality tennis, especially in the last set there were some amazing points. Sorry to Juan Martin, he's an amazing opponent and amazing player. In some ways he deserves victory too," a gasping Nadal said after setting up a blockbuster semi-final with Novak Djokovic.

"The last set had a little bit of everything, great points, great rallies, he was hitting crazy with his forehands. I tried to resist, maintaining focus. It's a day to be happy."

Del Potro threw everything he could at Nadal in a pulsating match and even conjured the shot of the tournament as he acrobatically dived to his right to hit a fizzing forehand volley that ended a spellbinding 23-shot rally.

Even then he was left flat on his stomach as his racket went flying out of his hand. He picked himself up and dusted himself down to play on for another eight games, but it was a different story an hour later when there was nothing left to fight for.

Victory secured, Nadal climbed over the net and ran over to the baseline to help the distraught Del Potro back to his feet. It was that kind of match.

"Rafa is a fighter. I was close to beating him and I couldn't. Sometimes you play your best tennis and it's not enough to beat him," said the teary-eyed Argentine, who has had the misfortune of running into Nadal at the French Open and Wimbledon championships over the past five weeks.

"He deserved to win today. After almost five hours, I fell down. I wanted to stay there for all night long. But Rafa came to me and we shared a big hug, and it was kind of him."

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A few hours earlier, however, it looked as if it was going to be 32-year-old Nadal who would end up down and out.

Just 90 minutes after defending champion Roger Federer was sensationally knocked out by South African Kevin Anderson, it seemed as if the grasscourt major would lose its top two seeds on the same day as Del Potro took a two-sets-to-one lead.

It was not as if Nadal was playing badly.

The world number one had lost only nine points on serve when, just before the ninth game of the second set, the result of Federer's shock demise was flashed up on the giant on-court scoreboard.

It was as if that out-of-the-blue news threw the Spaniard off his stride and he fluffed his lines to drop his serve.

The twice champion broke back but squandered four set points in the second set tiebreak, with a double fault on one of them. Del Potro made him pay as he pounced on his first chance to raise the prospect of another upset on day nine.

That blip was enough for Nadal, chasing an 18th Grand Slam title, to surrender his first set of the championships.

But the second seed stayed alive by taking the fourth set before the gripping drama continued in an electrifying deciding set in which both players were left diving after volleys and slipping over as they sprinted after blinding winners.

One such chase left Nadal toppling into the arms of a stunned woman sitting in the front row as he failed to put on the breaks as he dashed after a Del Potro smash.

That mishap could not stop Nadal from reaching his sixth Wimbledon semi-final and he celebrated the moment by raising both arms up into the skies after four hours and 48 minutes of thrilling action.

There was, however, one consolation for Del Potro who came off second best despite belting down 33 aces and producing 77 staggering winners, 10 more than Nadal.

"I think I won the best point of the match," the Argentine said with a rueful smile after being beaten by Nadal for the 11th time in 16 meetings.

The roaring Centre Court fans who gave him a standing ovation would not disagree.

(Reporting by Pritha Sarkar, editing by Ken Ferris) ((pritha.sarkar@thomsonreuters.com; +44 20 7542 7933; Reuters Messaging: pritha.sarkar.thomsonreuters.com@reuters.net;))