Federer failed to live up to his end of the bargain.
World number one Nadal, the 2010 and 2013 champion, brushed aside Russian 19-year-old Rublev 6-1, 6-2, 6-2 in just 97 minutes.
Nadal, a two-time U.S. Open victor, and Federer, a five-time champion, have never met at Flushing Meadows.
Does it really matter who Federer will face in the round of last eight?
The ruined possible first-ever NY matchup between Federer and Nadal, which had been a focus headed into the match, was an afterthought to Federer in the wake of a comprehensive loss.
Vandeweghe, having conquered her fear of majors, is inching ever closer to the head of the gifted USA women hoping to crack the Grand Slam code. No. 28 Kevin Anderson of South Africa.
Nadal crushed Alexandr Dolgopolov 6-2, 6-4, 6-1 in one hour and 41 minutes before Federer swept past Philipp Kohlschreiber 6-4, 6-2, 7-5 in an equally clinical fourth-round display.
Pliskova also played the first match on Arthur Ashe Stadium on Saturday. Federer's fans would cheer for del Potro's faults, considered bad etiquette in tennis.
"I think I got lucky", Del Potro said. "Del-po! Del-po!"
"We are from Spain and we always eat very late but of course I will be paying attention to it", Nadal said.
At one stage previous year, his world ranking, once as high as four in the world, slumped to 1,045 and he even considered retiring. The turning point was the third-set tiebreaker, which Federer was a single point from winning on four occasions.
The question was then whether Del Potro would retire. At 6-5, del Potro delivered a service victor. Dominic Thiem humiliated del Potro for two sets, but, with a frenzied crowd at his back, del Potro ultimately won in five.
She wouldn't have much problem if she plays as she did in a almost flawless fourth-round performance, looking nothing like the player who almost went home a round earlier.
"I have to work as hard as I can, and the main thing now is to try to keep working harder and harder, to improve, because I still have a lot of things to improve".
Even with Del Potro's stunning five-set win over Federer here in 2009 aside, when he captured his solitary major title, this rivalry has been full of brilliant battles.
"I can not believe to play another semi-final after all my injuries".
Federer said: "It's great to see him back on tour". Nadal looks to be playing well enough to stave off the young gun's challenge. "I wish him all the best".
Despite clearly being blessed with attacking weapons - 12 aces and 48 winners saw him past Goffin - Rublev will surely find that Nadal's defensive skills force his game to its limits and beyond.