Nadal could have gone up two sets to none after leading 6-3 in the tiebreaker.
"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.
Then Del Porto managed to hold serve to love, forcing Nadal to serve out the match, which he did, winning it 6-4 to reach his sixth semi-final. But the 6ft 6in Tower from Tandil proved the most stubborn of intruders, putting 33 aces on him in total.
Nadal got the first set, which consisted of long, close rallies, thanks to the only break in the 12th game to claim the opener 7-5.
They were soon back in the trenches, as one grinding rally followed another, each of them for a hint of weakness across the net.
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Trippier swung in a late free kick but Kane was unable to direct it on target and minutes later the match moved into extra time. Jordan Henderson is desperate to extend his record-breaking unbeaten run and help England reach the World Cup final.
"I wanted to stay there", del Potro said afterward, "all night long".
It was not as if Nadal was playing badly as he had lost only nine points on serve before heading into the ninth game of the second set.But just before that game started, Federer's shock demise was flashed up on the giant on-court scoreboard and it was as if that 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.
As Nadal looks ahead to the semi-finals, Del Potro heads for his next tournament.
"Well, at the moment I´m feeling sad after nearly five hours of running and playing this high level against the No. 1 in the world and losing", added Del Potro. It was so hard to stop him. There were no service breaks until the tenth game where Del Porto beat Nadal with a forehand victor to get the service break and set, 6-4. The result was far from certain.
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Knight's death came just days after 27-year-old Tyler Honeycutt fatally shot himself during a standoff with police on Friday. TMZ Sports reported Knight could've been sentenced for more than 50 years if he had been found guilty of all charges.
"In the end the court was a little bit slippery because the sun goes out and it was humid on the grass", Del Potro added. The shoes didn't do it.
'For the rest of the things, great news, semifinals of Wimbledon again.
But Del Potro ended the match flat on his face, the latest in a succession of slips, and Nadal explained that the conditions underfoot were to blame.
Del Potro finished with 77 winners to Nadal's 67 but failed to convert any of his five break points in the fifth set.
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After the win against Sweden , Bournemouth experienced a party atmosphere as thousands flooded into the streets. Bournemouth South Police said there will be three main road closures in the town centre at the end of the game.