David Ferrer retired in his final grand slam match as Rafael Nadal reached the US Open second round.
Back playing a grand slam for the first time in more than a year, Andy Murray came through the US Open first round.
Serena Williams continued her perfect record in the first round at the US Open after beating Magda Linette.
Simona Halep became the first top-seeded woman to lose in the opening round of the US Open.
Andy Murray will take on Fernando Verdasco in the second round at Flushing Meadows after seeing off James Duckworth.
Injuries have made 2018 a largely frustrating year for Stan Wawrinka, but he started the final grand slam of the season in style.
World number one Simona Halep was not feeling sorry for herself after her first-round loss in New York, saying it was "just a bad day".
Simona Halep was knocked out in the first round of the US Open for the second year in a row, losing to 33-year-old Estonian Kaia Kanepi.
After losing three finals previously on the WTA Tour, Aryna Sabalenka captured her maiden title by overcoming Carla Suarez Navarro.
Ivan Lendl has been hired by Alexander Zverev to help the German fulfil his promise on the biggest stages in tennis, the German says.