Novak Djokovic hinted an injury hampered him after he was stunned in the third round of Wimbledon by Sam Querrey.
Top seed and defending champion Djokovic came into the third major of the year with dreams of a calendar Grand Slam still alive, but he succumbed 7-6 (8-6) 6-1 3-6 7-6 (7-5) to the powerful American.
The Serbian had looked well off the pace on Friday, falling two sets down before rain meant the match would carry over to Saturday.
And though he was able to win the first four games upon play's resumption, further delays proved an advantage to 28th-seed Querrey, as he regrouped and sent shockwaves through SW19.
Asked if he was at 100 per cent in the match, Djokovic told a news conference: "Not really. But, you know, it's not the place and time to talk about it. The opponent was playing on a very high level and he deserved to win."
After confirming he will skip Serbia's Davis Cup tie with Great Britain, starting on July 15, Djokovic was again cryptic over his condition.
"I just said, I just don't want to talk about it. Please respect that. Thank you."
Djokovic also freely admitted that playing on Court One - rather than the scene of his three title wins, Centre Court - was influential in his defeat.
"[I am] more comfortable on Centre Court, obviously," he explained.
"I play 90 per cent of the matches on the Centre Court, 10 per cent on the other court. Obviously, naturally I'm going to feel better on the Centre Court.
"It's been a very successful year so far, but very long one, exhausting one, in every sense of that word. I just need some rest."