Commentator Darren Cahill said that the Argentine "looked like death" when he practiced during his off day in between a straight-set demolition of Roberto Bautista Agut and Monday's title with Thiem.
Can Del Potro come up with the goods, once again? I came here trying to play the best I can and then when I see this crowd cheering for me, I was trying to play better every game.
"He (Dolgopolov) is a player who can play fantastic shots but sometimes he can be very unpredictable so I just waited for my opportunity". The tall Czech had needed back-to-back three-setters to get to the last 16, including having to save a match point against Zhang Shuai of China in the third round.
These two players are not unknown to one another.
"Oh my God", Del Potro told the crowd.
Like everyone who faces Federer, del Potro will have to elevate his game to have a chance against the 19-times grand slam champion. A newfound energy guided him to another break of Thiem (pictured below) for 5-1 and all of a sudden the match was into a fourth set.
Juan Martin del Potro's stay at the U.S. Open really should be over.
Two days after fighting off a match point to advance, the No. 1 seed won 22 of 24 points on her first serve and broke her unseeded opponent's serve six times.
For Del Potro, beating Federer should have meant he had the world at his feet.
Del Potro must now try to recover for a quarter-final meeting with Roger Federer, who he beat to win his only grand slam title eight years ago.
Federer brings an 11-0 record against No. 33 seed Philipp Kohlschreiber into their night matchup.
Goffin's next match will be against 19-year-old Andrey Rublev of Russian Federation, who defeated Damir Dzumhur of Bosnia and Herzegovina 6-4, 6-4, 5-7, 6-4.
Understandably, given they have never met at the US Open before, there is a lot of focus on the fact that if Federer wins, and Nadal beats Andrey Rublev in his quarter-final, they will meet in the semi-finals on Friday.
The match victory was the 50th of Nadal's career at the U.S. Open.
No. 20-seeded CoCo Vandeweghe defeated No. 37 Lucie Safarova in straight sets 6-4, 7-6. In the victory, Federer won 88 percent of his first serve points and 73 percent of his second serve points.
"I think I played the best match of the tournament".
"He combines fantastic points with mistakes".
The 32-year-old is just the second qualifier to make the quarters in NY.
STATISTIC OF THE DAY: Big-serving Karolina Pliskova fired nine aces during her third-round win to take her tournament tally to 28, more than any other player in the women's draw.
The last time Nadal reached the quarterfinals in 2013, he won the second of his two U.S. Opentitles.
Now Nadal gets to play a fifth consecutive unseeded foe in Rublev, who took out No. 9 David Goffin 7-5, 7-6 (5), 6-3.