NEW YORK -- The closer Rafael Nadal gets to a potential long-awaited U.S. Open matchup with Roger Federer, the better he is playing.
Nadal easily returned to the tournament quarterfinals for the first time in four years by routing Alexandr Dolgopolov 6-2, 6-4, 6-1 on Monday.
Nadal turned in his most powerful performance yet on a dominant day for the No. 1 seeds, and he moved a victory away from the possible semifinal showdown with his longtime rival at the only major where they have never met.
"Every victory, every set that you win, is more confidence. That what's I am doing," Nadal said.
Nadal hadn't reached the quarterfinals in Flushing Meadows since the last of his two U.S. Open titles in 2013.
He advanced to face 19-year-old Russian Andrey Rublev, the youngest quarterfinalist since Andy Roddick had just turned 19 in 2001.
Rublev upset No. 9 seed David Goffin 7-5, 7-6 (5), 6-3. He will be Nadal's fifth straight unseeded opponent.
Later on Monday, Federer ousted No. 33 seed Philipp Kohlschreiber 6-4, 6-2, 7-5 to reach the U.S. Open quarterfinals. Federer took a medical timeout fore a sore back after the second set and otherwise showed no signs of trouble.
Federer did not face a break point and won in straight sets for the second time in a row, after being pushed to five sets in each of the first two rounds. He improved to 12-0 for his career against Kohlschreiber.
Federer is making his 12th U.S. Open quarterfinal appearance, which is tied with Ivan Lendl for third-most such appearances by a man in the Open Era -- trailing Jimmy Connors' 17 and Andre Agassi's 13, according to ESPN Stats & Information research.
Juan Martin del Potro came back from two sets to defeat No. 6 seed Dominic Thiem. He will face Federer in the quarterfinals. They met in the 2009 U.S. Open final, when del Potro won his only Grand Slam title and ended Federer's run of five championships in a row in New York.
"I took all that energy to change in a good way and think about (fighting) and not (retiring)," the 24th-seeded Argentine said. "Unbelievable atmosphere."
Del Potro long has been popular, but became even more so since returning from three operations on his left wrist that kept him out of Grand Slam action for two years and sent his ranking out of the top 100.
"He was gone for so long that it's just really nice to see him back playing these kind of matches," Federer said. "That's what he came back for, to get crowd support the way he got it."
Information from the Associated Press was used in reporting.