LONDON: The Wimbledon that just keeps on giving reached new levels of generosity on Friday as Novak Djokovic added another episode to the box-set of tennis epics and Andy Murray survived a fright to co-star in Sunday's series finale.

World number one Djokovic needed all his dexterity and self-belief to fend off the brutal groundstrokes of eighth seed Juan Martin del Potro, winning the longest ever Wimbledon semi-final 7-5 4-6 7-6(2) 6-7(6) 6-3 in front of a spellbound Center Court crowd.

Djokovic, whose career is littered with blockbusters against the likes of Murray, Rafa Nadal and Roger Federer, soaked up everything the burly Argentine threw at him for four hours and 43 minutes before coolly dispatching a backhand winner to reach his second Wimbledon final.

Home favorite Murray also reached his second final at the All England Club but put his legions of fans through the wringer again as fiery Pole Jerzy Janowicz threatened to incinerate his dream of becoming Britain's first male champion here since 1936.

From the moment 6ft 8ins Janowicz, Poland's first ever grand slam semi-finalist, launched his first 140 mph grass-charring serve Murray knew he was in for a hairy evening.

Ultimately the experience of 12 previous grand slam semi-finals helped him stay calm under fire to win 6-7(2) 6-4 6-4 6-3 in a match that concluded under the Center Court roof.

With Del Potro playing his best tennis since winning the US Open in 2009 and precocious 22-year-old Janowicz jumping the queue as the next big thing in men's tennis, the coming months look full of intrigue.

For now, though, it is all about Djokovic and Murray who, as predicted by many before a tournament laden with shocks and bizarre twists began, will face off for the 19th time on Sunday in their fourth grand slam final showdown.

The 26-year-old Djokovic had not been seriously tested en route to his 13th consecutive grand slam semi-final but against Del Potro he was stretched to breaking point.

Even before the incredible sinew-stretching 25-stroke rally that Del Potro won to save the first of two match points in the fourth set tiebreak the match had already transcended anything seen at the tournament.

When the Argentine, who seemed on the brink of retiring injured in the first game of his quarter-final against David Ferrer, leveled the match at two sets all the 15,000-capacity crowd, who for nearly five hours forgot about the day's supposed main attraction, roared its approval.

The psychological damage on Djokovic, who also squandered a break of serve in the fourth set, could have been terminal to his chances, especially with the memory of his five-set loss to Rafa Nadal in the French Open semis still fresh in the memory.

Instead, the ice-cool Serb just took a few deep breaths, got back to work and waited for the tiring Del Potro to crack, which he did in the seventh game when a weary backhand earned Djokovic the decisive break of serve.

SPORTINGLY APPLAUDED

After the final point, the warm embrace at the net said it all and Djokovic sportingly applauded Del Potro off the court.

“I have been pushed to the limit today,” said Djokovic, who is bidding to win the title for a second time.

“It was one of the most thrilling matches that I have ever played, especially here in Wimbledon.

“It was a cat and mouse game in a way throughout the match.

“You needed to stay committed and concentrated in order to wait for the chance. When it's presented, you have to grab it. I managed to do that in the fifth.”

Del Potro, who beat Djokovic at Wimbledon to win the bronze medal at last year's Olympics, was only the third Argentine to reach a Wimbledon semi-final, but at 24 he could return.

“You can see I play my best tennis ever on a grass court,” he said.

“But was not enough to beat the number one in the world. I was so close.”

Second seed Murray later said that Del Potro and Janowicz, big men with destructive power who move deceptively well, are the future of the game.

Janowicz, seeded 24 but destined for the top 10, clearly has an arsenal of weapons at his disposal, notably a first serve that topped out at 140mph and a withering forehand, but, at 22, is still to master the art of staying cool under pressure.

That said, he looked completely at home in the opening set of the biggest match of his career, matching Murray stride for stride before romping through the tiebreak.

Even after Murray took the second set Janowicz again responded to lead 4-1 in the third, but Murray, who was stretched to five sets by Fernando Verdasco in the quarters, showed all his experience to rattle off the next five games.

Murray's momentum was broken when fading light meant the roof had to be closed, but he returned under cover to topple the Pole and take his place in Sunday's showpiece.

“I think I'll be probably in a better place mentally,” Murray said of Sunday's final against Djokovic, who he beat in a memorable US Open final last year having lost to Roger Federer in the Wimbledon final.

“I've been there before. I won a grand slam. I would hope I would be a little bit calmer going into Sunday.”