Rafael Nadal and Angelique Kerber shrugged off sweltering temperatures to reach the US Open second round Monday as French Open champion Garbine Muguruza survived a worrying health scare.
Nadal, the 2010 and 2013 champion, took his perfect first round record in New York to 12-0 with a 6-1, 6-4, 6-2 win over Denis Istomin of Uzbekistan.
The Spaniard's reward for a fifth win in five meetings against the Russian-born player is a match-up with Italian veteran Andreas Seppi.
A wrist injury forced Nadal into an early retirement at the French Open and sidelined him from Wimbledon before a gold medal run in the doubles at the Olympics helped ease his misery.
"The most important thing is that I am here in New York. Injuries are part of the career. I had a hard time this year," said the fourth seed.
Kerber needed just over 30 minutes to get her pursuit of a first US Open title off to a winning start.
The second seed and Australian Open champion was leading Polona Hercog 6-0, 1-0 when the Slovenian called it quits, clearly wilting in the 33-degree heat, having won just nine points.
"It's not the way I wanted to win, but I am playing well and feeling good," said the German star.
Kerber, a semi-finalist in 2011, next faces Mirjana lucic-Baroni of Croatia.
Spanish third seed Muguruza carved out a gritty 2-6, 6-0, 6-3 win over Belgian qualifier Elise Mertens, ranked at 137.
But the French Open champion needed courtside treatment from a doctor after dropping the first set on the louis Armstrong Court.