Juan Martin del Potro sensationally gatecrashed the U.S. Open again on Wednesday, stunning five-time champion Roger Federer and shattering hopes of a first New York showdown between the Swiss legend and Rafael Nadal. The Argentine giant, who won his only Grand Slam title in the city in 2009 by beating Federer in the final after seeing off Nadal in the semis, triumphed 7-5, 3-6, 7-6 (10/8), 6-4 in front of a spellbound Arthur Ashe Stadium crowd.

The 28-year-old will once again face world number one Nadal in the semi-finals today, a stunning achievement for a man who had saved two match points to beat sixth seed Dominic Thiem in the last 16.

Nadal, who will keep his world number one status following third seed Federer's exit, had earlier defeated Russian teenager Andrey Rublev 6-1, 6-2, 6-2 in just 97 minutes. It will be a sixth U.S. Open semifinal for Nadal and 26th at the majors while Del Potro, the 24th seed, will be playing in just his fourth last-four match at the Slams.

For 36-year-old Federer, it was a first Slam loss of 2017 after he had captured the Australian Open and Wimbledon titles to take his career tally to 19. "I served really good. I hit my forehand as hard as I could and I played a great match. I deserved to win," said Del Potro, who will be in his first Slam semi-final since Wimbledon in 2013.

"This feels like my home court. I played Rafa here in 2009 too. Hopefully, I can get the same result on Friday."

Del Potro, whose career was almost ended last year after undergoing four wrist surgeries, wrapped up the first set thanks to a break in the 11th game secured with a blistering crosscourt pass. Federer had a 16-5 winning record over Del Potro ahead of the quarterfinal.

"It's hard to explain, I didn't play that badly," said Federer.

"I just ran into a guy who was better on the bigger points. I don't deserve to still be in the tournament."

Nadal will take an 8-5 record over Del Potro into the semifinal where the winner will face either Kevin Anderson or Pablo Carreno Busta for the title.

Now, Del Potro will be eyeing another Rafa-Roger double in New York as everybody thinks he has done it once so why can't he do it again, according to Reuters. When he won the U.S. Open title in 2009, the then 20-year-old Argentine beat Rafael Nadal and Roger Federer back-to-back to win his first grand slam title.

"Physically I'm not in the perfect conditions, but when you play semifinals of a grand slam, everything can happen, so you must be ready for the chance.

"Playing against Rafa in my favorite tournament, I will try to enjoy the atmosphere and the game." When they played in 2009, Del Potro smashed Nadal off the court with a blistering performance, dropping just six games.Meanwhile, the women's semifinals will be an all-American affair after CoCo Vandeweghe and Madison Keys set up a last-four duel. American 20th seed Vandeweghe claimed a 7-6 (7/4), 6-3 win over the Czech Republic's Karolina Pliskova, whose brief eight-week stay as world number one ended with Wimbledon champion Garbine Muguruza taking over.

Vandeweghe's victory means that the U.S. Open will have an all-American semifinal line-up for the first time since 1981 after Keys defeated Estonian qualifier Kaia Kanepi 6-3, 6-3.

The last time four U.S. women were in the semis was 36 years ago when eventual champion Tracy Austin, Chris Evert, Martina Navratilova and Barbara Potter all made it.

Keys, the 15th seed, will be playing in her second Slam semifinals after the 2015 Australian Open.