Rafael Nadal vowed to fight on and revive his faltering career after a shock US Open fourth round loss to Lucas Pouille condemned him to his worst Grand Slam season since 2004.

The 30-year-old Spaniard, the winner of 14 majors including two in New York, suffered a 6-1, 2-6, 6-4, 3-6, 7-6 (8/6) defeat to world number 25 Pouille in a four-hour last-16 epic.

Defeat means that 2016 will be the first year since 2004 that Nadal has not made a quarter-final of a Slam after a first round exit in Australia was followed by an enforced withdrawal from the French Open after the third round due to a wrist injury.

The same injury sidelined him from Wimbledon.

"I am close to being 100 percent again and I believe I can have a couple of more good years," said Nadal whose most recent Grand Slam title came with his ninth French Open in 2014.

His best runs since have been two quarter-final spots at the 2015 Australian and French Opens.

"I fought to the end today but I needed something that was not there. I will keep working to try and find it.

"I will keep working hard and I am motivated to do that."