- All four semi-finalists are aged 30 or over - the first time in the Open era that the men's singles semis at a Grand Slam have been contested exclusively by players over 30.
Nadal's reward is a place in the 28th Grand Slam semi-final of his career, and a 52nd showdown with long-time rival Novak Djokovic.
Nadal will next face Serbian star Novak Djokovic, who didn't quite have the same crowd admiration throughout his win over Kei Nishikori after appearing to lose his cool toward the chair umpire.
The match between American John Isner and Kevin Anderson of South Africa was tied at 24-24 in the fifth set - the second longest match in Grand Slam tennis history, prompting the Guardian to remark on the match, "Isner holds". He is one of the more complex players that I have ever seen in our sport, it is always a big test.
The length of the first semifinal means that Djokovic's matchup with Nadal will be played under the lights on Centre Court. With the Isner-Anderson match approaching a 40th game in the fifth set, Djokovic was playing with marbles in the locker room.
Djokovic's 2017 Wimbledon campaign ended in a quarterfinal retirement with an elbow injury which led to surgery and precipitated a worrying dip in form and confidence.
The Argentine next faces two-time champion Rafael Nadal, who has reached the Wimbledon quarterfinals for the first time since 2011.
"I didn't want to finish the match like that", said Del Potro, who hit 77 winners.
"It's feels great to be in the last four of a slam", the 12-time major victor said.
Both men are in the semi-finals at Wimbledon for the first time.
Kevin Anderson has won the first set of his Wimbledon semifinal against John Isner 7-6 (6).
"Of course I was anxious when I lost the second set", said Nadal, who had reached the quarter-finals without dropping a set and might have continued that run had he not squandered four set points, including one with a double fault, in the tiebreak.
The victor will automatically be favored against whoever emerges from the Kevin Anderson and John Isner match.
Isner had never got past the third round at Wimbledon before this year while a run to the last 8 at the 2011 US Open had been his previous best at the majors.
"I know he's playing very well", the Spaniard said.