US Open 2023
Venue: Flushing Meadows, New York Dates: 28 August-10 September
Coverage: Daily live text and radio commentaries across the BBC Sport website, app, BBC Radio 5 Live and 5 Sports Extra
Carlos Alcaraz had a short start to the defence of his US Open men's title after German opponent Dominik Koepfer retired injured midway through their first-round match.
The 20-year-old Spaniard led 6-2 3-2 when Koepfer, who rolled his ankle minutes into the match, had to stop.
Third seed Daniil Medvedev needed just 74 minutes to cruise into round two with a dominant win over Attila Balazs.
The 2021 champion hit 41 winners as he beat the Hungarian 6-1 6-1 6-0.
Despite his brilliant win on Arthur Ashe Stadium, the Russian said he "does not care" all the attention is firmly on top seed Alcaraz and 23-time major champion Novak Djokovic.
The emerging rivalry of top two seeds Alcaraz and Djokovic has dominated the build-up to the men's event.
Alcaraz won the US Open last year in the absence of Djokovic, who was not allowed to enter the country because he was not vaccinated against Covid-19, and beat the Serb at Wimbledon last month to win his second major title.
Tough challenges will lie ahead for Alcaraz as he looks to retain his New York crown and it was more straightforward than he would have anticipated against the unfortunate Koepfer.
Koepfer, ranked 75th, went over on his ankle in the first game of the match, needing a medical timeout and gamely continuing for an hour before deciding it was best to stop.
"That's not the best way to get through into another round, but I have to say on my side I was playing great," said Alcaraz, who will play South Africa's Lloyd Harris next.
"Honestly, I didn't expect to play such a great level in the first round.
"I am very, very happy with the level, even if Domi had to retire. Hopefully I can keep that level into the next round."
Medvedev, 27, will play Christopher O'Connell for a spot in the last 32 after he won an all-Australian encounter against Max Purcell.
But Medvedev's compatriot and 11th seed Karen Khachanov was upset 6-2 6-4 6-2 by American Michael Mmoh.
Dimitrov's fightback, Isner prolongs farewell
Elsewhere on day two, 19th seed Grigor Dimitrov produced an epic comeback as he saved three match points at two sets down against Alex Molcan of Slovakia.
The Bulgarian went on to win the five-set thriller 6-7 (9-11) 6-7 (5-7) 6-1 7-5 7-6 (11-9) in a marathon four hours and 40 minutes to set up a meeting with Britain's Andy Murray.
Veteran American John Isner beat Facundo Diaz Acosta of Argentina 6-4 6-3 7-6 (7-1) in his final tournament in professional tennis.
The 38-year-old, handed a wildcard entry at Flushing Meadows, announced last week he will retire after this year's event.
Isner served 11 aces in his victory over Acosta Diaz as he increased his record career tally to 14,422 .
Poland's Hubert Hurkacz, seeded 17th seed, overcame a two-set deficit to win 4-6 5-7 7-6 (7-0) 6-3 6-1 over Swiss Marc-Andrea Huesler and plays Britain's Jack Draper next.
Italian sixth seed Jannik Sinner cruised through in a 6-3 6-1 6-1 victory over Germany's Yannick Hanfmann.
Russian Andrey Rublev defeated Frenchman Arthur Cazaux 6-4 7-6 (7-5) 6-1, while 12th seed and 2020 finalist Alexander Zverev beat Australian Aleksandar Vukic 6-4 6-4 6-4.
Former Wimbledon finalist Matteo Berrettini beat French 29th seed Ugo Humbert 6-4 6-2 6-2.
The Italian will face another Frenchman in Arthur Rinderknech in the second round after he beat Argentina's Diego Schwartzman 6-3 6-4 6-2.
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