Swiss third seed Roger Federer barely escaped an upset bid from 70th-ranked US teen Frances Tiafoe on Tuesday before advancing 4-6, 6-2, 6-1, 1-6, 6-4 into the second round of the US Open.
The 19-time grand slam champion, who last lost in the first round of a major tournament at the 2003 French Open, will next meet either Russia's Mikhail Youzhny or Slovenia's Blaz Kavcic as he chases a record sixth US Open crown.
"It was more than a test. We enjoyed it out there, we kept fighting, trying and it was exciting," said Federer, who finished with 17 aces, 41 winners and 56 unforced errors.
"I had a slow start. I was worried about the back injury. In the fifth set, it was a coin toss and it went my way tonight so I am very happy."
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"I am feeling extremely well. This will give me great confidence," added Federer, who missed the 2016 tournament with injury and was playing under the US$150 million (Dh551m) Ashe roof for the first time.
Rafael Nadal took his US Open first-round record to 13-0 but Japanese teenager Naomi Osaka stole the headlines by knocking out defending champion Angelique Kerber as torrential rain caused more than 50 matches to be shelved Tuesday.
As players ran for cover from drenched outside courts where just 90 minutes of action was possible, and only three matches completed, Osaka's big-hitting game flourished under the roof of Arthur Ashe Stadium.
The world No 46, born in Japan to a Haitian father and Japanese mother, won 6-3, 6-1 as sixth seed Kerber became the first US Open women's defending champion to lose in the first round since Svetlana Kuznetsova in 2005.
World No 1 Nadal, meanwhile, began his campaign for a third US Open title with a 7-6, 6-2, 6-2 win over Serbia's Dusan Lajovic.
The 31-year-old Spaniard recovered from 3-5 down in the opening set against the 85th-ranked Lajovic, who has never won a match in New York.
"When I was down in the first set, I just tried to be there as he was playing well and controlling the points," said French Open champion Nadal, who is chasing a 16th major.
"But the end of the first set was very important. I got the break back and after that, everything changed."
Osaka, who surrendered a 5-1 final-set lead on the same court in losing to Madison Keys in the third round 12 months ago, fired 22 winners as Kerber went tumbling out of the world's top 10 as well as the tournament.
"At 4-1, I was hoping I don't do what I did last year," said Osaka, 19, who admitted suffering a brief flashback to her tearful loss to Keys.
Osaka will face either Sweden's Rebecca Peterson or Denisa Allertova of the Czech Republic for a place in the last 32.
"I just want to play good. I did that today and so I want to carry that into the next match," added the Japanese teenager, who secured her first career win over a top-10 player.
Kerber is the third top seed to go out in the first round after number two Simona Halep and seventh-seeded Johanna Konta lost on Monday.
"She just went for it," said 29-year-old German Kerber. "For sure, it was not the best day and not the best match for me."
US Open chiefs decided to cancel 44 singles matches and postpone the completion of 11 others until Wednesday because of the unrelenting rain.
In total, only nine singles matches were due to be completed out of a scheduled 64.
World No 1 Karolina Pliskova, bidding to back up her lofty status with a maiden first grand slam title, was able to make a winning start, courtesy also of playing under the roof on Ashe.
Czech 25-year-old Pliskova, the runner-up in 2016, eased past Poland's Magda Linette 6-2, 6-1 on the back of eight aces and 29 winners.
French Open champion Jelena Ostapenko downed Spain's Lara Arruaberrena 6-2, 1-6, 6-1 in a match relocated from Court 17 to Ashe.
The Latvian won 12 of the last 14 points to seal the deal in a tie suspended at 3-1 in the final set five hours earlier.