NEW YORK: Roger Federer shook off another slow start to defeat Bosnian Damir Dzumhur and reach the third round of the US Open on a rainy Wednesday where Kei Nishikori and Karolina Pliskova also advanced.
Swiss third seed Federer, a 20-time Grand Slam champion, fired 16 aces and rallied to dispatch 99th-ranked Dzumhur 3-6, 6-2, 6-3, 6-4 under the roof at Arthur Ashe Stadium.
Five-time US Open winner Federer, who lost to top-ranked Novak Djokovic in last month's epic five-set Wimbledon final, hasn't fallen in a Slam second round since 2013 at Wimbledon.
Federer, who also dropped the first set against Indian qualifier Sumit Nagal in his opener, struggled early but again answered the wake-up call after conceding the first set.
"Very similar to the last one," Federer said. "I tried to make less errors and be aggressive. It just takes me some time I guess."
He broke to 2-0 in the second set with a forehand winner and took the final game when Dzumhur double-faulted.
Federer broke again in the second game of the third set and rolled through, then blasted a forehand winner to break for a 2-1 edge in the final set and held from there to advance.
"I was able to save my serve after a sloppy first set," Federer said. "I came through. I buckled down and told myself I was going to hang tough and not get broken and that made a big difference."
Next in Federer's path is the winner of a later match between French 25th seed Lucas Pouille and Britain's 58th-ranked Dan Evans.
Defending champion Novak Djokovic and six-time US Open champion Serena Williams were set for later matches at Arthur Ashe Stadium.
US eighth seed Williams, seeking a 24th career Grand Slam title to match the all-time record won by Margaret Court, faces 17-year-old US wildcard Caty McNally.
Williams, 37, had won her first Slam title at the 1999 US Open and reached her second Flushing Meadows final before 121st-ranked McNally was born.
Djokovic, winner of four of the past five Slam titles and 16 in all, meets Argentina's 56th-ranked Juan Ignacio Londero in the other night feature. The Serbian star is trying to become the first back-to-back Open champion since Federer's run from 2004-2008.
Japanese seventh seed Nishikori, the 2014 US Open runner-up and a semi-finalist in 2016 and 2018, eliminated 108th-ranked American Bradley Klahn 6-2, 4-6, 6-3, 7-5 after two hours and 44 minutes.
Nishikori, who could face Federer in the quarter-finals, broke twice and took the first set in 28 minutes, but Klahn closed the second set with a break to level the match.
- 'Lost focus' -
Nishikori dominated from there until serving for the match up 5-1 in the fourth set. Klahn saved a match point in the seventh game and won 12 of 15 points, then denied another Nishikori match point and held serve to 5-5.
But Nishikori held again, seized three more match points, and finally capitalized on the last of them when Klahn smacked a backhand beyond the baseline.
"A little bit of lost focus after 5-1," Nishikori said. "He started playing better too."
Next in Nishikori's path will be either Australian Alex de Minaur or Chilean 31st seed Cristian Garin.
Czech third seed Pliskova, seeking her first Grand Slam title and the world number one ranking, ousted 202nd-ranked Georgian qualifier Mariam Bolkvadze 6-1, 6-4 in 66 minutes.
"It was a solid performance," Pliskova said. "I didn't have to play the best today."
Pliskova, the 2016 US Open runner-up, will next face either Tunisia's Ons Jabeur or Aliaksandra Sasnovich of Belarus.
Pliskova needs to reach at least the quarter-finals to have a chance at becoming world number one. Defending champion Naomi Osaka and reigning Wimbledon champion Simona Halep must win the title.
French Open champion Ashleigh Barty, the second seed from Australia, has the inside track in the chase for number one, thanks to Osaka defending more points from her win last year.
Barty was set to play 73rd-ranked American Lauren Davis later. The Aussie could meet Serena Williams in the quarter-finals.
Also advancing was Ukrainian fifth seed Elina Svitolina, who beat seven-time Grand Slam champion Venus Williams 6-4, 6-4.