Wimbledon champion Novak Djokovic suffered in sweltering US Open conditions Tuesday but battled through to the second round with a 6-3, 3-6, 6-4, 6-0 victory over Hungarian Marton Fucsovics.
Djokovic, playing his first match on Arthur Ashe Stadium since falling to Stan Wawrinka in the 2016 final, received a brutal welcome back to Flushing Meadows as soaring temperatures and high humidity prompted organisers to offer the men a 10-minute mid-match heat break for the first time ever.
Roger Federer, the second seed, escaped the worst of the conditions as he headlined the night session on Ashe. Nor did he meet much resistance from Japan's Yoshihito Nishioka in a 6-2, 6-2, 6-4 victory.
Up 5-1 in the final set, Federer was unable to close out the match against Nishioka's serve, and then was broken on his first attempt to serve it out.
Fourth-seeded German Alexander Zverev kept his time in the sun to a minimum with a 6-2, 6-1, 6-2 victory over Canadian lucky loser Peter Polansky.
And Australian Nick Kyrgios fired 25 aces in a 7-5, 2-6, 6-4, 6-2 victory over Moldova's Radu Albot.
In the women's circuit, Petra Kvitova beat Belgian Yanina Wickmayer 6-1, 6-4 and Madison Keys downed France's Pauline Parmentier 6-4, 6-4.
Maria Sharapova, who won the last of her five Grand Slam titles in 2014, advanced 6-2, 7-6 (8/6) over Patty Schnyder, out of retirement and at 39 the oldest player to qualify for a Grand Slam main draw.