Not only did Federer push boundaries with his play and set a plethora of records, he also became one of the most popular players tennis has ever seen.
His style of play - described as balletic, graceful and fluent - has endeared him to millions of fans across the world. So too has his polite and charming personality.
Federer transcends tennis. For some, he almost transcends the world.
Before the match, you could see hundreds of fans filing into the arena wearing Federer-branded clothing and accessories.
Hats, T-shirts, scarves, banners and even custom-made earrings. All red and white - the national colours of Switzerland - with most emblazoned with the initials of their hero: RF.
A few Swiss flags were also draped around the indoor arena.
One Federer super-fan at the O2 Arena, Robert Springer from Poland, described his idol as the 'King of Tennis".
"He has quality, empathy, a super sportsman, a gentleman and a good father. Plus he always has time for his fans. He's the one and only," Robert told BBC Sport.
Tickets for the night session on Friday were already sold out before Federer announced last week he was going to retire after the annual team event.
Initially they were available from between £40 and £510. Following the news, they were being offered on resale platforms for over £1,000 each.
Despite the match finishing at 00:26 BST, with the celebrations continuing for about another half an hour, few of those present left before the end.
"Thank you everybody. I've had so many people cheer me on and you guys here tonight mean the world," said Federer, who later added he was "really scared" about speaking on court because he knew he would get emotional.
"This is not the end-end, you know, life goes on. I'm healthy, I'm happy, everything's great, and this is just a moment in time."
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