Novak Djokovic insists he will come back stronger than ever after Sam Querrey ended the world number one's bid for tennis immortality in one of Wimbledon's greatest upsets.

Djokovic arrived at the All England Club last week hoping to win a third successive Wimbledon title and move a step closer to winning the first calendar Grand Slam since 1969.

But instead Djokovic trudged off Court One humiliated after the big-serving Querrey's 7-6 (8/6), 6-1, 3-6, 7-6 (7/5) third round victory condemned the Serb to his earliest Wimbledon exit for eight years.

It was an astonishing result for the 29-year-old, who had won the last four majors and reached the quarter-finals of each of the previous 28 Grand Slams.

Yet rather than conduct a depressing post-mortem of his first defeat in 31 Grand Slam matches, Djokovic did his best to accentuate the positives of his incredible run, claiming he would be back to his best in time for the Olympics and then the US Open in August.

"I believe in positive things in life. I managed to win four Grand Slams in a row. I want to try to focus on that rather than on failure," he said.

"Certainly it's not the first time that I'm losing in a Grand Slam match, or any match for that matter. I know what to do.

"It's disappointing, of course. Losing at a Grand Slam hurts more than any other tournament. There is no doubt about that.

"I'm not happy to lose a match. But I'm going to move on from this hopefully as a stronger player."

Djokovic faced a barrage of questions about his strangely lethargic effort against Querrey and he hinted he had been suffering from mental and physical fatigue following the French Open.

Having beaten Andy Murray in Paris to win the last major title missing from his trophy cabinet, Djokovic conceded the fulfilment of a long-held ambition had made it harder to motivate himself at Wimbledon.

"It's an amazing feeling to be able to hold four Grand Slams at the same time. But coming into Wimbledon, I knew that mentally it's not going to be easy to kind of remotivate myself," he said.

"The importance of this tournament is so immense that you always find ways to try to give your best.

"Obviously my best wasn't enough this year."

Although the match played over two days due to a series of rain delays, Djokovic said the weather wasn't a factor.

However, he did admit he felt completely out of sorts making a rare appearance outside of Centre Court.

"It's really not necessary to talk about the rain interruptions and the conditions. It's the same for both of us," he said.

"I play 90 percent of the matches on the Centre Court, 10 percent on the other court. Obviously I'm going to feel better on the Centre Court.

"I don't want to take anything out of victory for my opponent. He played a terrific match.

"He served very well. That part of his game was brutal. He just overpowered me."