World number one Novak Djokovic admitted he was struggling to come to terms with his stunning first-round exit from the men's singles tournament at the Olympic Games in Rio de Janeiro.
Djokovic's bid for singles gold at Rio 2016 was swiftly ended by a resurgent Juan Martin Del Potro on Sunday, upstaged 7-6 (7-4) 7-6 (7-2).
Winner of 12 grand slams, Djokovic was no match for Del Potro and he was visibly emotional, walking off Centre Court in tears.
Speaking afterwards, Djokovic said: "No doubt this is one of the toughest losses in my life and in my career.
"It's not easy to handle, especially now, just after the wounds are still fresh. But you have to deal with it.
"It's not the first or the last time I am losing a tennis match. But the Olympic Games, it's completely different."
Djokovic, who lost to Del Potro in the bronze medal match at the London Games in 2012, produced a trademark gritty performance in Brazil.
The Serb star, though, was unable to find an answer to Del Potro's attacking prowess as the Argentinean continued his rise following wrist problems in recent years.
Despite the heartbreaking loss, Djokovic had nothing but praise for his close friend, who will face Joao Sousa in Tuesday's second-round meeting.
"Delpo was the better player and he just deserved to win. That's sport. He just came up with some extraordinary tennis and I have to congratulate him," Djokovic added.
"I'm very sad and disappointed from my side to go out in a tournament this early, but on the other hand I'm glad a good friend of mine, and somebody who has struggled the last couple of years with injuries, is back and playing at this level."