No matter how it ends, both men will always have their spot in one of the most memorable matches in the storied history of the All England Club.
Slugging back and forth over a semifinal-record 4 hours, 43 minutes of backbreaking tennis Friday, top-seeded Djokovic emerged with a 7-5, 4-6, 7-6 (2), 6-7 (6), 6-3 victory to move one win away from his seventh major title.
"One of the most epic matches I've played in my life," Djokovic said.
On Sunday, Djokovic will play second-seeded Andy Murray, who defeated No. 24 Jerzy Janowicz 6-7 (2), 6-4, 6-4, 6-3 to make his second straight Wimbledon final and move one win away from becoming the first British man in 77 years to capture his country's home tournament.
This will be their third meeting in the last four Grand Slam finals. Murray won at the U.S. Open last year and Djokovic won in Australia this year. On Murray's mind every bit as much, however, will be his 7-5, 7-5 win on Centre Court last year in the Olympic semifinals.
"I'll take that thought to my head when we play on Sunday," Murray said.
With skies starting to darken, the Murray match was interrupted for a half-hour while the roof was closed over Centre Court. Murray protested the delay, saying there was still sunlight left. He had other reasons, too. He had just rolled off five straight games to close out the third set after falling behind 4-1.
"It's a tough situation," Murray said. "There were probably 45 minutes of light left. I'd like to think this is an outdoor event and you try to play as much as you can outdoors. But I managed to regain focus. I took a shower, talked to the guys a little bit and got back to it."
The late finish came courtesy of what had been billed as the undercard, but turned into something much better. Del Potro and Djokovic played the longest semifinal in Wimbledon history. The match came up only five minutes short of the 2008 five-set final between Roger Federer and Rafael Nadal that's generally considered the greatest match played on Centre Court -- and perhaps anywhere.
Djokovic and del Potro spent the entire, sundrenched afternoon exchanging huge groundstrokes, long rallies and even a few laughs during their marathon, which covered five sets, 55 games, two tiebreakers and 368 points.
"I think this match is going to be memory for a few years," del Potro said. "We play for four hours and a half on a very high level. We didn't make too many errors. I don't know if the rest of the players can play like us today."
Eighth-seeded Del Potro, back in a Grand Slam semifinal for the first time since winning the 2009 U.S. Open, saved two match points in the fourth-set tiebreaker, then won the final four points to take it 8-6.
Shortly after, the match hit the 4-hour mark, guaranteeing it would surpass the 1989 match between Boris Becker and Ivan Lendl -- a 4-hour, 1-minute affair -- as the longest semifinal in Wimbledon's long history.
It's not the first time Djokovic has been involved in one of these. His 2012 Australian Open victory over Nadal lasted 5 hours, 53-minutes. Only a month ago, Nadal outlasted Djokovic at Roland Garros in a semifinal that went 4 hours, 37 minutes.
"When you feel good physically, when you know you're fit and you don't feel a huge fatigue, that gives you mental confidence, obviously," Djokovic said.
Sliding on the grass-turned-dirt behind the baseline, doing the occasional splits and, at one point, diving for a shot, then laying on the ground, face-down in despair, Djokovic put on a stellar show, filled with 80 winners but also lots of counterpunching, always making his 6-foot-6 opponent hit one more shot.
Despite the pressure of the match, both players took it for what it was: sports entertainment at its finest. Del Potro played to the crowd and also exchanged a few fun back-and-forths with his opponent. In the sixth game of the fourth set, the Argentine chased down a drop volley and flicked a forehand down the line. His momentum carried him to the other side of the court and the shot was called out.
Should he challenge?
"He asked me, What's going on?' I said, `Listen, if I was you, I would challenge," Djokovic recounted. "He said, `No, but you know it's out and don't waste my challenge.' I said, `OK, you decide whatever you want. But truly, I'm not lying to you."
All this was done with smiles on their faces. Del Potro opted against the challenge but won the fourth set anyway, putting his 4-6 lifetime record in five-setters against Djokovic's mark of 18-7.
Djokovic's fitness played a big role in landing him the decisive break in the fifth set.
It came with del Potro serving behind 4-3. With the score 15-all, Djokovic hit a drop shot-lob combo to close out a breathtaking 22-shot rally. Del Potro dropped his hands onto his knees and clearly hadn't regained his wind on the next point, when he sliced an easy backhand into the net. Two points later, Djokovic had the break, and the 5-3 lead.
He saved a break point in the final game by hitting an off-balance drop shot winner off a del Potro serve return that clipped the net cord. Two points later, Djokovic had his 53rd career win on grass -- 24 more than del Potro.
"You can see I played my best tennis ever on grass court," del Potro said, "but was not enough to beat the No. 1 in the world. I was so close."
It was quite a taxing stay at Wimbledon for del Potro, who came into the semifinal with his left knee heavily taped, a victim of two nasty slips that sent him tumbling earlier in the tournament. The second fall came two days earlier, on the fifth point of his quarterfinal against David Ferrer. Del Potro said the trainer gave him a couple of "magic pills" -- anti-inflammatories -- and that kept him going in his straight-sets win over the No. 4 seed.
Against Djokovic, del Potro showed few signs of an aftereffect.
Tested throughout by a variety of Djokovic drop shots, del Potro got to most. More than once, the Argentine did his impression of a lanky golden retriever -- chasing the tennis ball from wide of the court on the forehand side to wide of the court on the backhand side. After going wide in the third set to hit one of his 48 winners, del Potro stood on the ledge separating the court from the stands, waiting for a high-5 from one of the fans at courtside.
The fans soaked in the del Potro experience, cheering on the underdog as he pushed the world's best player to the limit.
"They help me a lot for fight, to keep trying, keep going," del Potro said. "Of course I'm sad now, but in a couple of days, I will see how big the match was."
Midway through the fourth set, Del Potro lost his serve to fall behind 4-3, but broke right back, finishing the game with a big backhand winner, a guttural grunt and a fist pump.
They held serve until the tiebreaker, and when del Potro won that one, he looked like the del Potro of 2009, the man who broke the Federer-Nadal-Djokovic stranglehold on the majors by overcoming a 2-1 deficit against Federer in the 2009 final at Flushing Meadows to win the title.
If he stays healthy, he'll certainly be someone to contend with two months from now in New York.
But this week, it's Djokovic playing for a title after putting on one heck of a show.
"I know that I have been pushed to the limit today, as my opponent was also," Djokovic said. "It was one of the most thrilling matches that I have ever played, especially here in Wimbledon."