Roger Federer promised his fans they had not seen the last of him after bringing the curtain down on his glittering career, saying he would see them on a "different type of tennis court" in future.

The Swiss 20-time Grand Slam champion and Rafael Nadal lost their Laver Cup doubles match 4-6, 7-6 (7/2), 11-9 to Team World's Frances Tiafoe and Jack Sock.

The defeat for Europe left the two teams locked at two points apiece after the first day of the Ryder Cup-style event at London's O2 arena.

But the match itself was ultimately a sideshow on an emotional occasion for the 41-year-old, who made a lengthy and tearful address to the crowd, his rivals and family afterwards.

"This is not the end-end, you know, life goes on," he told a post-match press conference in the early hours of Saturday, having recovered the poise that was the hallmark of his career.

"I'm healthy, I'm happy, everything's great.

"The message from me was just making sure I relay my passion for the sport to the fans, and I let them know that hopefully we'll see each other again on a different type of tennis court somewhere around the world," he added.

"I have no plans whatsoever, where, how, when. All I know, I would love to go and play places I have never played before or go say thank yous for years to come to all the people that have been so supportive of me."

Federer, who had not played tennis competitively since Wimbledon in 2021 due to a knee injury, said at times during the build-up to the match, which started late on Friday, he had been "horribly nervous".

"The last two days have been tough, you know, to say the least," he said. "Thankfully in moments I totally forgot about it, slept great, everything was wonderful, I could enjoy it, I feel.

"And because of that I think I will be able to have a better recollection of how it went, because if it's all just stress throughout and I want it to be only perfect, I know I will remember half of it."

- 'Super-emotional' -

Nadal also admitted it had been a tough day, with a "super-emotional" ending.

"For me it has been a huge honour to be a part of this amazing moment of the history of our sport, and at the same time a lot of years sharing a lot of things together," he said.

"When Roger leaves the tour, an important part of my life is leaving too."

Federer and Nadal, who have won 42 Grand Slam singles titles between them, spoke warmly of their friendship even though they have been fierce rivals for nearly two decades.

"It's been great," said the Swiss. "I think we enjoy each other's company, and we have so much to look back on, but also just enjoy spending time together.

"We have a million topics to cover. I always feel like any evening we ever spend together we never have enough time."

Nadal, 36, said his relationship with Federer had been a "super-long and positive journey".

"For me was always the guy to beat," said the Spaniard. "So at some point we were probably the biggest rivals -- I think always in a very good way.

"We respect a lot each other, families, teams. I mean, we never had big issues... I mean, when we were getting older, I think every year the personal relationship gets better and better."

"Very proud to be part of his career in some way," he added. "But even for me happier to finish our career like friends after everything we shared on court like rivals."