Rafael Nadal emotionally says, "A significant portion of my life is leaving too." after Roger Federer's retirement. 

Rafel Nadal and Roger Federer beaten 4-6, 7-6 (2), 11-9 by Jack Sock and Frances Tiafoe

Players at Laver Cup pay tribute to Federer after his final game

As Nadal sat alongside his friend and great rival at the O2 Arena on Friday night, the pair cried

In one of the fiercest rivalries in sports, Federer and Nadal faced off 40 times. The most notable encounter was the nail-biting 2008 Wimbledon final, which Nadal won in the deciding set. It continues to be regarded as one of the best tennis matches ever played.

Federer, a former world number one and a player who will be remembered as one of the greatest champions of any sport, described his 25-year professional career as a “perfect journey.”

There is no ideal goodbye. After 14 months of trying to make a comeback as a full-time player, Federer entered the O2 Arena physically weakened, and he later admitted that he wasn't always sure he'd be in good enough shape to play doubles.

But by the time it was through, it didn't matter. He has already sacrificed a great deal for both himself and the sport, and at the age of 41, he retires with a career that is as full as any.

“I was able to remind myself always on the court again how wonderful this is,” said Federer. “This is not the end-end – life goes on. I’m healthy, I’m happy, everything’s great, and this is just a moment in time.”