US Open 2017: Roger Federer wins in five sets as Rafael Nadal also comes from behind
|Venue: Flushing Meadows, New York Dates: 28 Aug-10 Sept|
|BBC coverage: Live radio and text commentary on selected matches every day.|
Roger Federer was taken to five sets for the second time in three days before overcoming Russia's Mikhail Youzhny at the US Open.
The five-time champion was two sets to one down but eventually came through 6-1 6-7 (3-7) 4-6 6-4 6-2 in New York.
Federer has now won all 17 matches against Youzhny, a year younger at 35, since the pair first met in 2000.
Top seed Rafael Nadal required four sets to see off Japan's Taro Daniel in the night session.
The Spaniard, 31, trailed by a set and a break before two fizzing forehands turned the second set around and he went on to win 4-6 6-3 6-2 6-2.
"It's true that I didn't play very well tonight but at the same time it's true that I'm through to the next round," said the two-time champion.
Nadal will play Argentina's Leonardo Mayer in the last 32.
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Federer takes the long route
It is the first time Federer has played five-set matches in the first two rounds of a Grand Slam.
"I think because you're on a high, you're thrilled that you got through, so you don't look at the negative," he said.
"Or I don't. Yes, I might feel more tired than I normally would going into a third round, but that's OK.
"My preparation hasn't been good at all here. I knew I was going to maybe struggle early on. Maybe I struggled more than I would have liked to.
"But I'm still in the draw, which gives me a chance."
The Swiss third seed goes on to face Spanish 31st seed Feliciano Lopez in round three at Flushing Meadows.
'This match wasn't about the back'
Federer remains unbeaten in Grand Slam play this year, having won his 18th and 19th major titles at the Australian Open and Wimbledon, and skipped the French Open.
However, Federer's preparation for Flushing Meadows was disrupted by a back injury and he has been taken to the limit in his opening two matches.
American teenager Frances Tiafoe forced a fifth set in Tuesday's night session, before Youzhny led by two sets to one on Thursday afternoon.
"This match wasn't about the back, which is good. This is more just a grind," Federer said after winning in three hours and eight minutes.
"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."
After breezing into a 4-0 lead, the errors began to flow from Federer's racquet.
His backhand, such a strength for much of the year, was particularly wayward and he finished with 35 errors off that side in a total of 68.
It was a poor forehand that allowed Youzhny back into the match as the Swiss served for a two-set lead, and it was a battle to the finish line from then on.
The Russian levelled in the tie-break and drew gasps from the 23,000 spectators as a forehand brought him the decisive break in the third.
A woeful Federer volley into the tramlines seemed to sum up his afternoon, but the 19-time Grand Slam champion gathered himself sufficiently to edge through.
After an early break in the fourth set he again failed to serve out, but this time responded in the next game to level when a Youzhny backhand flew wide.
The Russian was having his own problems by now, requiring visits from the doctor in the fourth and fifth sets and falling to the court, apparently with cramp, early in the decider.
A tired double fault saw Youzhny fall behind at 4-2 and Federer quickly saw the match out against an opponent now unable to move freely, finishing with a smash.
"I haven't played a lot of guys with cramps in the last decade or so and the rules have changed, you're not allowed to get any help from the physio," added Federer.
"We've played a bunch of times and this was probably our best match."
BBC tennis correspondent Russell Fuller
Federer maintains this match, which evolved from an exhibition into a gripping drama before Youzhny's cramp set in, was "not about the back".
As he did after his first-round five-set win, Federer struck a confident note in interviews, stressing the belief that his rhythm will return as the tournament progresses.
For the moment, he is winning more sets than he is losing, but his form is far from convincing.
Playing 10 sets in the opening two rounds is incredibly rare for an eventual champion, but as this is Federer - a man who won three five-set matches in the second week of the Australian Open - then never say never.