A deflated Novak Djokovic blamed a bad day at the office for his stunning second-round elimination by Uzbek wildcard Denis Istomin which condemned the Serb to his earliest grand slam exit in nearly a decade.
A strangely off-colour Djokovic bowed out 7-6(8) 5-7 2-6 7-6(5) 6-4 at Rod Laver Arena, the court where he won his sixth title last year and was widely tipped to clinch a record seventh in 10 days' time.
As the match slipped beyond the second seed's control, Djokovic could conjure little emotion to rally in the fifth set but he denied that his competitive fires were lacking in the stunning upset.
"There was intensity, of course," he told reporters.
"We played four-and-a-half hours. It's just that, you know, it's one of these days when you don't feel that great on the court, don't have much rhythm, and the player you're playing against is feeling the ball very well.
"So, you know, that's sport.
"I started the season very well. Again, it's a tennis match. On a given day, you can lose. I mean, nothing is impossible.
"What can I do? I did try my best till the last shot, but it didn't work."
After winning his maiden French Open to complete a sweep of grand slam titles, Djokovic's form fell away in the second half of last season, prompting queries about his motivation leading into the new season.
Those queries looked to be put to bed after he opened his season with victory at the Qatar Open, having beaten world number one and long-time rival Andy Murray in the final.
He opened his Australian Open campaign with an impressive straight sets win over Spanish veteran Fernando Verdasco, who knocked out compatriot Rafa Nadal in last year's first round at Melbourne Park and had held five match-points over the Serb in Doha.
But the manner of Djokovic's exit in Melbourne, where he has reigned supreme for most of the last decade, raised fresh doubts about the Serb's mindset.
He said he had not had time to reflect on his mental state but conceded that it was not his physical fitness that wanting against Istomin on a mild afternoon at Melbourne Park.
"Of course, four-and-a-half hours is not easy on the body. But still, I don't think that has affected neither me or my opponent," he said.
Still raw from the loss, Djokovic gave short shrift to a query about his playing schedule.
"At the moment I just want to go home, spend time with my family, and that's all," he said, adding that the defeat was hurting him as much as any in the past.
"Of course. I'm not used to losing in Australian Open second round. I've always played so well," he said.
"Throughout the last 10 years, I've won six titles here. This court has been so nice to me. I enjoyed it very much.
"Of course, it's disappointing. But the end of the day I have to accept it."
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