US Open 2018: Stan Wawrinka beats Grigor Dimitrov in straight sets
Swiss wildcard Stan Wawrinka beat eighth seed Grigor Dimitrov 6-3 6-2 7-5 in the first round of the US Open at Flushing Meadows in New York.
2016 champion Wawrinka had two knee operations last year and was unable to defend his title in 2017.
It is the second consecutive Grand Slam in which Wawrinka, 33, has beaten Dimitrov in round one, having come from a set down to win at Wimbledon in July.
Dimitrov converted only one of eight break points on Arthur Ashe Stadium.
"The last time I played on this great court I won the title, so it was great to be able to come back and play again," said Wawrinka.
"The level was really high. There were lots of emotions out there. It's always tough to play your best in the first round."
Three-time Grand Slam champion Wawrinka - ranked 101st in the world - will face Frenchman Ugo Humbert in the second round.
Elsewhere, 31st seed Fernando Verdasco beat fellow Spaniard Feliciano Lopez 6-2 7-5 6-4 to set up a second-round meeting with Britain's Andy Murray,who defeated Australian James Duckworth 6-7 (5-7) 6-3 7-5 6-3.
Wimbledon semi-finalist John Isner, the 11th seed, saw off fellow American Bradley Klahn 7-6 (7-3) 6-3 6-4.
Canadian 25th seed Milos Raonic beat Argentine Carlos Berlocq 7-6 6-4 1-6 6-3 to set up a tie with Frenchman Giles Simon, while Australian world number 98 Jason Kubler defeated 19th seed Roberto Bautista Agut 6-3 6-3 6-4.
There was an emotional and premature end to the match between Canadian teenagers Denis Shapovalov and Felix Auger-Aliassime.
Auger-Aliassime, 18, received medical treatment during the first third-set changeover, complaining that his heart was racing. He retired after playing two more games with Shapovalov leading 7-5 5-7 4-1.
Shapovalov, 19, consoled his compatriot as they walked off the court.
The victor said: "I hope he recovers quick. I told him at the net we will play a lot of times and we'll play in the final one day."