Rafael Nadal insists his wrist injury is slowly improving as he prepares to face Denis Istomin in the US Open first round.

The Spaniard returned from the problem at the Olympics, winning a doubles gold medal at Rio 2016 and reaching the semi-finals in singles.

Nadal, who won the last of his 14 grand slams at the French Open in 2014, said the injury was getting better, albeit slowly.

"Well, I am better. I am a little bit better. It's obvious that when you have been out for two and a half months you need a little bit of time," the 30-year-old said.

"I tried to go quickly, especially in the Olympics and then competing last week in Cincinnati, but the wrist still bothers me a little bit.

"It's true that the wrist bothers me a little bit less every day. I need to understand again how to hit my normal forehand.

"During the wrist injury always you try to find movements to avoid the pain.

"I think today I can start the forehand, I think my normal forehand, but it still needs time to feel that I am more confident on my wrist. But I am practicing well and I am competing well, I think."

Novak Djokovic and Andy Murray have seemingly put a gap between themselves and fellow 'Big Four' members Nadal and the injured Roger Federer.

Nadal said there was no doubt the top two had created some distance, mainly due to his and Federer's injury woes.

"The 'Big Four', as you say, are getting older. It's normal that there is a new generation that tries to be in those positions, no?" he said.

"But still Novak is number one, Andy number two, and he's in a good position in the race. I got injured, it's true.

"But before the injury I was the third in the race… and not very far from number two. Roger, it's true, is having a tough year in terms of injuries, too. Making two tournaments, Australia, Wimbledon. Let's see.

"It's obvious that we will not be here forever. It's true that Andy and Novak today are creating distance from the rest.

"At the same time, it's true I have been injured and Roger, too, no? Let's see. I am excited about this part of the season."