World number one Novak Djokovic began his US Open campaign with victory over Poland's Jerzy Janowicz - despite the Serb requiring treatment to his arm. Djokovic, who has struggled with a wrist injury, won 6-3 5-7 6-2 6-1 after calling the trainer in the first set. Spanish fourth seed Rafael Nadal beat Uzbekistan's Denis Istomin 6-1 6-4 6-2. Djokovic had spoken ahead of his opening match about the left wrist injury that has hampered him since the Olympics, but it was the right arm that appeared to be troubling the Serb against Janowicz. He called a medical timeout after the fifth game to allow the trainer to work on his elbow and upper arm, but promptly broke the Janowicz serve on his way to the first set.
On calling for the medical timeout, the Serb said: "It was just prevention. It's all good. It's getting better and better each day. Hopefully as the tournament progresses, I'll reach my peak. There are periods when you're not feeling 100% but I don't think it's necessary to talk about this now. I'm just glad to come through this day and let's keep on moving." A wildly uneven display from both men saw Janowicz level at one set all after Djokovic double-faulted and blazed a forehand wide, shaking his right arm in apparent discomfort. The defending champion began the second set serving at below 90mph but Janowicz was too inconsistent to take advantage, and Djokovic eventually ran out a comfortable winner - at least in terms of the scoreline. He goes on to face Jiri Vesely in round two - the Czech who beat him in Monte Carlo earlier this year.
There was an early shock in the men's draw as Britain's Kyle Edmund upset French 13th seed Richard Gasquet 6-2 6-2 6-3. John Isner, the 20th seed, almost followed Gasquet out of the tournament but the American came back from two sets down to beat 18-year-old compatriot Frances Tiafoe 3-6 4-6 7-6 (7-5) 6-2 7-6 (7-3). "It hurts, it hurts a lot," said Tiafoe, who served for the match in the fifth set. "Especially not getting over the line." Nadal, who missed the French Open and Wimbledon with a wrist injury, said after his win: "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." Women's third seed Garbine Muguruza of Spain avoided an upset as she fought back to beat Belgian Elise Mertens 2-6 6-0 6-3. Olympic champion Monica Puig was beaten in her first match since winning gold in Rio, going down 6-4 6-2 to China's Zheng Saisai.