Del Potro eases in to last 16 with straight sets win over Verdasco and last year's finalist Anderson is also through
Rafael Nadal battles into US Open fourth round after epic clash with Karen Khachanov
World No 1 and defending champion Rafael Nadal came back from a set and break down to defeat Karen Khachanov 5-7, 7-5, 7-6, 7-6 and reach the US Open fourth round on Friday.
Victory for the 32-year-old Nadal put him into the last 16 in New York for the 10th time and on course to add to his 2010, 2013 and 2017 titles.
However, 2009 champion and third seed Juan Martin del Potro, his potential semi-final opponent, also made the last 16 with a 7-5, 7-6, 6-3 win over Fernando Verdasco.
Top seeded Nadal defeated Khachanov after an epic four hour, 23 minute struggle on Arthur Ashe Stadium, but the 22-year-old Russian had his chances.
He served for a two sets to love lead in the 10th game of the second set and had set point in the fourth-set tiebreaker.
Nadal, seeking an 18th major, will face Georgia's world No 37 Nikoloz Basilashvili for a place in the quarter-finals.
The Georgian won just one game in a three-set loss to Nadal in their only previous meeting at Roland Garros last year.
Basilashvili reached the last-16 of a Slam for the first time by seeing off Argentina's Guido Pella 6-3, 6-4, 1-6, 7-6.
"Karen played well. He's improving always. He's young. He has everything. I really see him winning a lot of matches in his career," Nadal said. "For me personally, it was a physical, demanding match."
Khachanov, 22, and bidding to make the last 16 of a grand slam for the third time this year, took the opener before Nadal needed strapping applied to support his right knee in the changeover.
"I am going to be at 100 per cent for the next match," he assured reporters.
The top seed was quickly down 3-1 in the second set before battling back to 4-4. Khachanov cracked when serving for a two sets lead in the 10th game.
Nadal took advantage with a love service hold and a break to level the contest just moments after the roof was closed.
A thrilling tiebreak settled the third set with Nadal clinching it after a lung-busting 39-shot rally on a fifth set point. But the drama wasn't over as Nadal was broken in the 10th game of the fourth set as he served for the match
He then had to save a set point in the 12th game before cruising through the tiebreaker to claim his 25th win against just one loss since mid-May.
"I gave everything I had. Just a few points difference and it could go another way. Big respect to Rafa. That's why he's No 1, such a great fighter," said Khachanov.
Del Potro is into the last 16 for the sixth time after seeing off Verdasco, the man who ended Andy Murray's grand slam return in the previous round.
The tall Argentine will next face Croatian 20th seed Borna Coric who made the last 16 of a grand slam for the first time with a 6-3, 7-5, 6-2 victory over Russia's Daniil Medvedev.
South Africa's Kevin Anderson, who was runner-up to Nadal last year, outlasted Canadian teenager Denis Shapovalov 4-6, 6-3, 6-4, 4-6, 6-4 as the roof on the new Louis Armstrong Stadium was closed for the first time.
"Felt like being in a coliseum. Constant noise going on the whole time," said Anderson after his second five-setter in three rounds.
The fifth seed, runner-up to Novak Djokovic at Wimbledon, next faces ninth-seeded Austrian Dominic Thiem, who made the last 16 for the fourth time in five years with a 3-6, 6-3, 7-6, 6-4 victory over American Taylor Fritz.
Thiem has now put together three wins in a row for the first time since finishing runner-up to Nadal at Roland Garros.
John Isner, the last American man standing, fired 34 aces, 85 winners and saved the three break points he faced in beating Serbia's Dusan Lajovic 7-6, 6-7, 6-3, 7-5.
He will face Milos Raonic who put out 2016 champion Stan Wawrinka 7-6, 6-4, 6-3.