Roger Federer said letting slip two championship points in his Wimbledon final loss to Novak Djokovic was "such an incredible opportunity missed".
The Swiss, 37, led Djokovic 8-7 40-15 on his serve in the final set but the Serb fought back to win 7-6 (7-5) 1-6 7-6 (7-4) 4-6 13-12 (7-3) in four hours and 57 minutes.
Victory for Federer would have given him a ninth Wimbledon singles title.
"I don't know what I feel right now... I can't believe it," said Federer.
"You just always try to push yourself to see things on the better side. But it was definitely tough to have those chances."
Federer also held two break points when Djokovic served at 11-11 in the deciding set but could not convert them.
It was the longest singles final in Wimbledon history and the first fifth-set tie-break to be played in a Wimbledon final.
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It is the second time Federer has been involved in the longest singles final at Wimbledon - and ended up losing too - after he was beaten by Rafael Nadal in 2008.
Federer has lost his past five meetings with Djokovic in Grand Slams, last beating the Serb at Wimbledon in 2012.
He still holds the all-time men's Grand Slam record of 20 singles titles but Djokovic now has 16 with Nadal on 18.
"It used to be a really, really big deal, I guess when you were close," Federer said of the overall record.
"I guess two behind, then eventually you tie, then eventually you break. That was big.
"It's been different since, naturally because the chase is in a different place.
"I take motivation from different places. Not so much from trying to stay ahead because I broke the record, and if somebody else does, well, that's great for them. You can't protect everything anyway."
Federer, who during Wimbledon set two new landmarks in winning his 100th match at the championships and his 350th match at a Grand Slam, said holding the record was not what motivated him as a player.
"I didn't become a tennis player for that," said Federer.
"It's about trying to win Wimbledon, trying to have good runs here, playing in front of such an amazing crowd in this Centre Court against players like Novak and so forth.
"That's what I play for."
Federer said there were similarities with his loss to Nadal in 2008 but differences too.
"This one is more straightforward maybe in some ways because we didn't have the rain delays, the night coming in and all that stuff," he said.
"But sure, epic ending, so close, so many moments, sure there are similarities.
"I'm the loser both times, that's the only similarity I see."
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Three-time Wimbledon champion Boris Becker: "All the compliments in the world to Roger Federer, for the performances over the past two weeks, showing he's still one of the top players in the world, and one point away from a record ninth Wimbledon title.
"He's an ambassador for all men, not just sportsmen, he's in great shape.
"We said before that the longer the match goes on, the better it would be for Djokovic. But Roger was as fit as a fiddle in the fifth set."
Former British number one Tim Henman: "There's no doubt Roger Federer will be massively disappointed.
"In terms of disappointments in his career this will be right up there. To have two match points and against one of his biggest rivals on his favourite court - it will hurt.
"I know he's good at controlling his emotions, but this will sting for a long, long time."