The No. 3-seeded Federer won five consecutive U.S. Open championships from 2004-08 and also was the runner-up twice, including two years ago.
"Oh, my God", del Potro told Shriver.
"Feel like I would probably win it somehow because I should have been up maybe two sets to love". "I just had all these chances". He looked fine when he came back out for the third set.
Del Potro looked like a superstar on that night in NY and it looked as if he had arrived as a serious player at the top of the game.
In inflicting Thiem with his first loss from two sets up at a slam, Del Potro proved that it's not just his deadly forehand but arguably the biggest heart in tennis that threatens to bring Federer unstuck once again.
However, bolstered by the crowd, del Potro reeled off eight of the next 10 games to force a fourth set.
But Nadal went back to work on Labor Day in the round of 16 and was his ruthless best again as he demolished the always risky and acrobatic Alexander Dogopolov 6-2, 6-4, 6-1. The Serb, despite five US Open final defeats, is himself a two-time champion in NY. Williams managed to win the season-opener Australian Open in Melbourne despite being eight weeks pregnant, defeating her sister Venus in the finals.
Federer's win saw him set up a quarter-final clash against Juan Martin del Potro in what will be a repeat of the 2009 decider, which the Argentinian won.
World No.1 Rafa Nadal has given Russian teenager Andrey Rublev a tennis lesson to race into the semi-finals of the US Open and a possible showdown with Roger Federer.More news: Deondre Francois' knee injury very bad in so many ways
Dolgopolov, who has been interviewed by anti-corruption investigators about a match with unusual betting patterns last month at another tournament, was hesitant to give Nadal too much credit. Nadal needed one hour, 36 minutes to dispatch Rublev, who showed he's not quite ready for the grand stage. He finished with 11 aces to Kohlschreiber's four, while winning 88 percent of his first-service points, per the tournament's official website.
"First quarterfinal, he made more mistakes than usual, " Nadal said.
"He's a player who can play fantastic shots but sometimes he can be very unpredictable with errors so I just waited for my opportunity".
"He combines unbelievable points with mistakes".
"I'm very happy to get through. I think it would be good for the game".
Nadal hadn't reached the quarterfinals in Flushing Meadows since the last of his two U.S. Open titles in 2013. Further, Federer returned to a more aggressive posture, charging the forecourt with more determination than he had in his first two matches.
Others who previously reached the men's quarterfinals are American Sam Querrey, Kevin Anderson of South Africa, Pablo Carreno Busta of Spain and Diego Schwartzman of Argentina. The No.16 seed took out Maria Sharapova in the round of 16 to reach her second consecutive quarterfinal in NY. Earlier, No. 20 CoCo Vandeweghe knocked off top-seeded Karolina Pliskova 7-6 (4), 6-3.
But can she fight off American powerhouse CoCo Vandeweghe, a player that is firing all cylinders in NY?