Rafael Nadal made up for lost time with a dominant start to his US Open campaign in New York.
The 2010 champion was playing his first match at Flushing Meadows for two years after missing last year's tournament during his seven-month break with knee problems.
Nadal took on America's Ryan Harrison in the first round and was never really troubled in a 6-4 6-2 6-2 victory.
The Spaniard said: "I missed a lot of places last year. Always when you miss a tournament like the US Open, it's not good news.
"So for me the chance to be back here playing is great. I enjoyed the week before when I was practising. The first match after two years on Arthur Ashe is a great feeling."
Hard courts have been Nadal's most troublesome surface, both results-wise and for his suspect knees, but he has been flawless this year, winning three Masters series titles.
He went into the US Open on a 10-match winning streak after back-to-back trophies in Montreal and Cincinnati, which included victories over Novak Djokovic and Roger Federer.
Djokovic is a narrow title favourite but Nadal is considered by many the man to beat - and he will not be enlisting the help of any special diets.
Djokovic believes his switch to a gluten-free diet was crucial in his elevation to the best player in the world and he has recently published a book on the subject.
Andy Murray briefly tried the same diet but Nadal will not be following suit.
He said; "At the end of the day, all the small things can help if you don't go crazy. I always had the theory that the most important thing is to be happy, enjoy what are you doing, and be fresh mentally.
"If you have the gluten-free diet or have the perfect diet and it's a big sacrifice for you and that results in you not being happy the rest of the day, not being fresh mentally because that's a lot of effort for you, it's better not to do it.
"If you feel that's the right thing to do to be fit, do it. It's not a secret, and there's not only one way to be a good tennis player or to be fit. Everybody's different.
"Now it seems like the gluten-free diet is great. After three years or four years we will find another thing that will be great, too. Then the gluten-free will not work anymore.
"So all these kind of things that are news, personally I am not doing. I am happy with the normal diet."
The big upset of day one came early on when British qualifier Dan Evans knocked out 11th seed Kei Nishikori 6-4 6-4 6-2.
The 23-year-old next meets Australian Bernard Tomic, who was a break down in the fourth set against Albert Ramos before turning things around to win in five.
Eighth seed Richard Gasquet eased past American Michael Russell 6-3 6-4 6-2 but 30th seed Ernests Gulbis, who beat Murray in Montreal, and 27th seed Fernando Verdasco both lost five-setters.
Fourth seed David Ferrer has not been in good form since the clay-court season so a 7-5 6-3 6-2 win over 18-year-old Australian qualifier Nick Kyrgios was a morale-boosting result.
World number one Djokovic begins his campaign on Tuesday in the night session against Lithuania's Ricardas Berankis while fifth seed Tomas Berdych takes on Paolo Lorenzi of Italy.