One GOAT to another: You challenged me, beat me a lot... made me enjoy the game even more

Farewells, as they say in professional sport, are hard.

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But farewells can be beautiful too, as two men who redefined modern tennis have shown.

A couple of years after Rafael Nadal joined Roger Federer in his last tournament to create scenes that still lie fresh in memory the two sitting next to each other, hand in hand, sobbing along as Federer's farewell video played out - it was Federer's turn to evoke emotions in Nadal's final act.

Through the eloquence of words.

On a day Nadal turned up to compete as a professional tennis player in his final tournament, representing Spain in their last eight Davis Cup Finals clash against Netherlands in Malaga, Federer put out a lengthy, moving letter on social media for his good friend and great rival.

"As you get ready to graduate from tennis, I've got a few things to share before I maybe get emotional," Federer wrote.