LONDON - Novak Djokovic won the longest men's semi-final in Wimbledon history to defeat Juan Del Potro 7-5, 4-6, 7-6 (7-2), 6-7 (6-8), 6-3 and reach his 11th final at a grand slam. The No. 1 Serb, Wimbledon 2011 holder, refined his skills as a marathon man with his victory in four hours, 43 minutes. The epic was played a year and a half after he needed almost six hours in Melbourne to defeat Rafael Nadal for the Australian Open trophy. The Djokovic-Del Potro match beat the previous mark for a men's semi at the All England club of four hours, one minute set in 1989 by Ivan Lendl and Boris Becker. It was the longest time ever on court for Del Potro, who came to the contest with a damaged left knee but showed no signs of discomfort. "This was one of the best matches I've been a part of," said the top seed. "It was one of the most exciting, it was so close, nothing could separate us." Djokovic ended with 22 aces to four for his Argentine opponent, with the Serb producing 80 winners and breaking on three of 15 occasions against a ferocious Del Potro defence. Del Potro saved a pair of match points in the fourth-set tiebreaker, the first a 34-stroke monster which left the South American leaning on his racquet and gasping for breath. The match carried on into the deciding fifth, as afternoon turned into early evening. Djokovic secured a break for 5-3 from a Del Potro forehand that went wide, but then had to come from 0-30 as he tried to serve out the win. The top seed, playing his 13th consecutive grand slam semi, set up a third match point and came good with his backhand winner to end it. "I was so close to be at the finals here in Wimbledon,"said Del Potro. "But I knew my opponent. I think I played really good tennis during four hours and a half, but he played better because he won the match. "It was a really high-level match. He hits so hard the ball. It was unbelievable to watch, but, of course, I'm sad because I lost and I was close to beating him." Djokovic agreed with that assessment: "I played well except for maybe when I was up two sets to one and a break and dropped serve," said Djokovic, who now leads the series with Del Potro 9-3. "But that's why he's a champion, He fought for everything. In tough situations he comes up with unbelievable shots. "I didn't play wrong when I had the match points, but I should have been more aggressive. Credit to him for fighting so hard. I'm very proud to go through." Added Djokovic: "I came out ready for five sets. I stayed tough and solid to the end. "I didn't expect anything less, to be honest, because I was playing a player who didn't drop a set throughout the tournament, as I did. A very great quality player, a grand slam winner. We were both feeling very confident on the court. It was never going to be a straight-set match." Neither man had dropped serve coming into the match. Del Potro was looking to become just the second Argentine man to reach the Wimbledon final after David Nalbandian in 2002, while Djokovic was aiming for a place in his 11th Grand Slam final.