The two sporting legends joined Vasek Pospisil to share their love for tennis on Tennis United.
The World No.1 has signed players such as Grigor Dimitrov and Dominic Thiem to join the four-city series, which will be played behind close doors.
Family and famed rivals inspired former No. 1.
The German, speaking to Lareus.com, says that as long as Serena Williams is playing, she can win.
The Frenchman has released a single on Apple Music and Spotify.
Serena will guest on Yahoo's Reset Your Mindset live stream.
The American was a rising force in the game when injuries took her out of it.
