Their baseline exchanges were lengthy and intense, accompanied by loud grunts of exertion and exhaustion, punctuated by the thud of racket string against tennis ball.
In the end, as he almost always does lately, Djokovic displayed the stamina and fortitude to win a long-as-can-be match, edging del Potro 7-5, 4-6, 7-6 (2), 6-7 (6), 6-3 Friday to close in on a second Wimbledon championship and seventh Grand Slam title overall.
"Unbelievable to watch," said del Potro.
"Draining," said Djokovic, who has won 10 of his last 12 five-setters. "One of the most exciting matches I've ever played in my life."
Folks around here felt just as euphoric about Friday's second semifinal, even if it was far less competitive or compelling. Britain has waited 77 years for one of its own to claim the men's trophy at Wimbledon, and for the second consecutive year, Andy Murray is one victory away. He came back from a set down, then a break down in the third, and got past 24th-seeded Jerzy Janowicz of Poland 6-7 (2), 6-4, 6-4, 6-3 in a match that concluded with Centre Court's retractable roof shut.
"I was very relieved after the semis last year, whereas this year ... I was a bit happier," said Murray, who lost to seven-time champion Roger Federer in the 2012 final. "I'll be probably in a better place mentally. I would hope so, just because I've been there before."
On Sunday, the top-ranked Djokovic faces No. 2 Murray, the third time in the past four Grand Slam tournaments they will meet in the final. The exception was last month's French Open, which Murray skipped because of a bad back.
Last September, Murray defeated Djokovic in five sets at the U.S. Open to earn the first major title anywhere for a British man since Fred Perry at that tournament in 1936 — months after Perry's historic win at Wimbledon. In January, Djokovic beat Murray at the Australian Open. Now they'll settle things at the All England Club.
Born a week apart in May 1987, and with similar styles that rely on terrific returning and successful defence at the baseline, they are creating a growing rivalry, one that could someday belong alongside Djokovic vs. Rafael Nadal, and Nadal vs. Federer. Federer, Nadal and Djokovic divvied up 31 of the last 33 Grand Slam titles. The exceptions were at Flushing Meadows, for Murray in 2012, and del Potro in 2009.
On Friday, with warm temperatures and the court bathed in sunlight, Djokovic and del Potro produced a contest worthy of two major champions — the longest semifinal, by time, in Wimbledon history. Theirs also was the first Wimbledon semifinal in the 45-year Open era between two men who hadn't dropped a set in the tournament.
Del Potro won the last time they played, in March, and also the only other time they faced each other at the All England Club, for the bronze medal at last year's London Olympics. But neither of those was at a Grand Slam, and Djokovic plays his best when the stage is the biggest.
A harbinger of things to come, the first set was as tight as could be for 11 1/2 games and 52 minutes, packed with thunderous strokes by both men — the crowd gasped loudly at some of the hardest — and Djokovic's trademark scrambling, sliding defence. His legs stretched so far, he often did the splits; sometimes, he slipped and fell.
Del Potro covered plenty of ground, too, his tall frame carrying him to balls most men couldn't reach, even though his left knee was heavily wrapped in white tape because he hyperextended it during a tumble in the third round.
And then, in a four-point blink with del Potro serving while down 5-4, the opening set changed. Djokovic's relentless defence kept forcing del Potro to hit an extra shot, and from 30-love, Djokovic hit a backhand winner and used a drop shot that drew a netted reply, then watched as del Potro missed a backhand long and a forehand wide.
"I hit many winners in one point," del Potro lamented later, "and always, the ball comes back."
But he did not despair. He kept coming, earning a break and taking the second set, providing plenty of entertainment along the way.
When his momentum from chasing a backhand carried him all the way to the stands, del Potro stood on the green wall and high-fived a spectator. After diving for a volley, he stayed down on his back, arms and legs spread far apart, then waved his hands over his chest, as if to say, "No mas!"
Midway through the fourth set, Djokovic hit a drop volley that del Potro reached for a down-the-line forehand. The ball landed near a line and was called out. Del Potro walked around the net and approached Djokovic, then the two pals smiled while chatting.
"It was (up) him to decide if he wanted to challenge or not," recounted Djokovic, the 2011 Wimbledon champion. "I said, 'Listen, if I was you, I would challenge.'"
The back-and-forth ended with del Potro playfully yanking the zipper on Djokovic's shirt.
"He's a good guy, a good friend of mine," del Potro said. "We have a fantastic relationship. But when we are playing, we want to win, for sure."
Djokovic was ever-so-slightly better, surprisingly hitting more aces, 22-4. Repeatedly, Djokovic managed to return del Potro's fast serves.
There were so many important shots at important moments. One came in the third-set tiebreaker, which Del Potro led 2-1. From there, though, Djokovic won the next six points, including at 3-2, when del Potro hit one overhead smash that was retrieved, then hit another that landed in the net while Djokovic fell.
When Djokovic blocked a half-volley backhand winner to end the set, del Potro bowed his head, then pulled his white shirt over his face.
In the fourth set, with del Potro looking gassed and a step late, Djokovic broke to lead 4-3. Things were looking bleak for del Potro, but he summoned something extra to break right back, only the second time — and the final time — he would win a game served by Djokovic.
In that set's tiebreaker, Djokovic went up 6-4 with a forehand winner, earning two match points. On the first, a 25-stroke exchange, del Potro hit one of his violent, flat forehands, and Djokovic responded with a lob that landed a tad long. Del Potro waved at the ball, pleading for it to go out, then leaned over, sucking air. On the second, del Potro produced a forehand winner. He would take the next two points, too, to force a fifth set.
"It was about the nerves, and Nole handled it much better at the end," said Djokovic's coach, Marian Vajda, using his player's nickname.
Djokovic got the last break he would need when del Potro sailed a running forehand long to make it 5-3. Del Potro shielded his eyes with his left palm, and Djokovic bent over, chest heaving, knowing he was one game away. Wouldn't be easy, though. Nothing was on this day.
Del Potro pounded a forehand for a break point, and a chance to extend the match, but Djokovic answered with a winner of his own. A service winner set up Djokovic's third match point, and this time he made it count, delivering a backhand winner down the line.
They hugged at the net, and Djokovic put a hand on the nape of del Potro's neck, consoling him.
"I know that I have been pushed to the limit today," Djokovic said. "This is where your physical strength, but also mental ability to stay tough, can decide the winner."
Murray is undoubtedly stronger, physically and mentally, today than earlier in his career, when he lost his first four Grand Slam finals.
Including his London Olympic gold medal, Murray has won 17 grass-court matches in a row, and 23 of 24. He hung in there when Janowicz was smacking hard serves and taking a 4-1 lead in the third set.
At 4-2, 30-all, though, Murray hit a forehand that clipped the top of the net and trickled over, setting up a break point. Janowicz then tried a drop shot, and Murray made a long run to reach the ball for a cross-court forehand winner. That was part of a five-game run that gave Murray the third set and momentum — and pumped up the partisan fans.
"Everything basically collapsed after this one point," explained Janowicz, the first Polish man in a Slam semifinal.
Past 8:30 p.m. at that point, the tournament decided to close the roof and turn on the artificial lights, a half-hour break Murray argued against. When play resumed, though, he was far better.
Now Murray has time to think about facing Djokovic and the possibility of a Wimbledon championship.
"I might wake up on Sunday and be unbelievably nervous, more nervous than I ever have been before," Murray said. "But I wouldn't expect to be."
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