Rafael Nadal believes he is making improvements despite suffering a shock third-round loss to Fabio Fognini at the US Open.

World number eight and 14-time grand-slam champion Nadal went down 3-6 4-6 6-4 6-3 6-4 as Fognini claimed an incredible victory from two sets down at Flushing Meadows.

The loss marked Nadal's first defeat from two sets up in a best-of-five contest and ensured the Spaniard will end the year without a slam title for the first time since 2004.

But Nadal still found some solace in his ability to keep fighting until the finish.

"He's a player with a great talent, with huge shots, and he played amazing shots," he said. "But what I am doing worse is playing worse than what I used to do the last couple of years. That's it.

"We can be talking for one hour trying to create a reason. But the sport for me is simple, no? If you are playing with less confidence and you are hitting balls without creating the damage on the opponent that I believe I should do, then they have the possibility to attack.

"It's another loss. My mind allows me to fight until the end. That us something that I was missing for a while, that feeling that I am there.

"For the nerves, for the anxiety that I had for a long time this season, I was not able to do it. I was not able to be fighting the way that I was fighting today. So it's an improvement for me. I take that like a positive thing and I know what I have to do. I am going to work on it.

"[I have to] Accept that was not my year and keep fighting until the end of the season to finish in a positive way for me."