Rafael Nadal was pleased with the standard of his play early in Monday's US Open victory over Borna Coric and revealed he had to battle with physical issues and dehydration during the win.
Competing in the tournament for the first time since winning in 2013, Nadal came through 6-3 6-2 4-6 6-4 against Coric - exacting a measure of revenge following defeat to the Croatian teenager in Basel last year.
However, the 14-time grand slam winner says he was delighted with his display against Coric, given the physical problems he encountered late on.
"I think I played great. The first two sets I played a very high level of tennis," explained the Spaniard.
"Seriously, then I get a little bit tired. I had some problems. I was sweating a lot. I lost little bit. I don't feel strong enough after that.
"I had little bit of stomach problem so I felt not perfect, physically perfect then. It was just a little bit of dehydration. Was very humid tonight out there. I was sweating a lot. Sometimes happens this these days.
"But then in the fourth I recovered little bit. I played again more aggressive. Finally was important victory for me. Happy the way that I played when I was physically good."
A wrist injury meant Nadal was unable to defend his title last year, with the 29-year-old having experienced mixed form on the ATP World Tour this season.
However, he refuted suggestions that he was eager to make up for lost time in New York, adding of his 2014 absence: "It is not the moment to think about that.
"It was tough to miss last year because the opportunity of 2014 will not be back. So that's an opportunity lost.
"But that's part of my career, too. I had few opportunities lost during my career. But at the same time, I converted more than I expected."