Meanwhile, Serena Williams crushed older sister Venus 6-1, 6-2 in a shockingly subdued third round clash to stay on track for a record equaling 24th Grand Slam title, Reuters reported.
Not since 2011 has Nadal lost to a Russian but his string of 16 victories stretching back to 2011 looked ready to end along with his US Open title defense when big-hitting Khachanov came out with guns blazing.
The 27th seed kept up the pressure throughout a four hour, 23 minute thriller that was the Spaniard’s longest ever match at Flushing Meadows.
“I am very happy to be through in a very tough situation,” Nadal said in an on-court interview.
“There were some tough moments during the match, but he played aggressive. There are things to work on for the next round, but the good thing is I have a chance to improve.”
After coasting through his first two matches, Nadal appeared poised for another uneventful day against a 22-year-old he had beaten four times without dropping a set.
Flat family tie
Serena Williams said her win over sister Venus on Friday was more meaningful than those she scored when they were up-and-coming teenagers because the pair realize they only have a limited number of years left in the game.
Serena, who will be 37 next month, showed her 38-year-old sister no mercy to continue her quest at Flushing Meadows to tie the record for most Grand Slam titles.
“I feel like we want it so bad now,” a reflective Williams told reporters.
“I mean, we wanted it really bad when you were younger but we had a lot more years in our future,” she said.
“Now, I mean, we definitely want to continue to play, but it’s not like we’re 18 and 19 anymore. So it’s a little bit different.”
The sisters first met as professionals at the 1998 Australian Open when Serena was 16 and Venus 17 and have played a total of 30 times, with the younger sibling coming out on top in 18 of those matches.
Serena called her sister the best player she has ever competed against and called the win a high point as she battles back to full fitness after having her first child a year ago.
“I played much better tonight than I have since I started this journey on my way back,” said Williams, who made the Wimbledon final in July.
The meeting between the famed tennis siblings had been hyped as the biggest night of the US Open but turned into a flat, uninspired spectacle as Serena simply outclassed her sister.
The only moment of suspense in a contest all but devoid of drama came in the second game when Serena rolled over on her ankle, drawing gasps from the sellout crowd.
“I roll my ankles a lot so I just wanted to get it taped as tight as I could for the rest of the match and see how I feel tomorrow,” Serena said in an on-court interview.
“This was my best match since my return. I’ve worked really hard for it ... and hopefully everything will keep paying off,” she added.