Roger Federer was taken to five sets for the second match running at the US Open, eventually ousting 35-year-old Russian Mikhail Youzhny 6-1 6-7 (4-7) 4-6 6-4 6-2.
Federer, who was pushed to the brink by American teenager Frances Tiafoe in round one, has now been taken the distance in his opening two matches at a major for the first time in his illustrious career.
Leading 6-1 5-3 on the Arthur Ashe Stadium, the Swiss almost appeared too comfortable against an opponent he had never lost to in 16 previous meetings.
For an hour, Youzhny, a former top 10 player, struggled to win games, though this was a refreshing reminder of how the sport can turn in a flash.
A unusually sloppy game from Federer when serving for a two-set lead was punished, and the Russian snuck in to edge a second set tie break.
From there, Youzhny stunned Federer with a combination of aggressive and measured tennis, mixing up his game with some crisp groundstrokes and zippy slice backhands.
The Swiss made an extraordinary 68 unforced errors in the 3 hours and seven minute contest, while Youzhny was affected by cramp in the fourth and fifth sets.
Federer, the eloquent mover he is, didn’t appear to be struggling physically following his back problem in Cincinnati early this month.
"It wasn't about the back"
"This match wasn't about the back, which is good. This is more just a grind," Federer said after the match.
"I felt different, completely different, the way it played and everything. But I'm really, really happy I got through.
"These five-set battles are actually quite a lot of fun and I feel quite warmed up by now," he quipped.
Federer will now meet 31st seed Feliciano Lopez in the third round, a player he has never lost to in 12 previous matches.
Straight forward early on
Against Youzhny, Federer established a 5-0 lead in under 15 minutes and two games later the first set was on the board.
The Russian broke Federer for the first time to go 2-0 ahead at the start of the second set, however the Swiss then won five of the next six games, allowing him to serve for the set.
That was when the match turned and, after leveling the contest at a set apiece, Youzhny found a new lease of life.
The Russian didn’t face a break point in the third set and served it out to 0 when the pressure could have consumed him.
Youzhny runs out of gas
Federer showed little signs of angst throughout the match, however he was treading dangerous tides against the inspired Youzhny.
The Swiss couldn't serve out the fourth set at 5-3 but managed to avert the danger by breaking his ailing opponent in the following game.
Youzhny hung on at the start of the decider but pulled up when running for a drop shot.
He soldiered on, with his movement hampered, however he could no longer match Federer from the baseline.
The nineteen-time grand slam champion has dodged another bullet but is still searching for his top form in New York.