'You beat me -- a lot': Roger Federer, Serena Williams react to Nadal's potential final match

The King of Clay has possibly made his final farewell as a pro.

Rafael Nadal played in what could be his final match on Tuesday, falling in straight sets 6-4, 6-4 to Botic van de Zandschulp in the first singles match of the Davis Cup, to cap an extensive career that included 22 Grand Slams.

Though a victory from Nadal's teammate Carlos Alcaraz kept their squad alive, even if Spain also wins the doubles match to advance, Nadal said after his defeat he would not select himself to play in the semifinal round. Such a decision would be left to Spanish captain David Ferrer, if needed.

Legends from the tennis world were quick to speak up and pay their respects to Nadal's potential last hurrah. Led by Roger Federer and Serena Williams, here are the top reactions from across the sporting world:

Why am I getting so choked up. With @RafaelNadal retirement. I'm not good at goodbyes

Thank you for giving everything, @RafaelNadal. pic.twitter.com/Cvye6Lpt20