Who is the greatest tennis player of all-time? The U.S. Open is underway, and that means it's time to rank the best tennis players ever. From Serena Williams to the Big Three of Roger Federer, Rafael Nadal and Novak Djokovic, SI Top 10 lists the greatest to ever hold serve on the court. Who do you think is the GOAT of tennis? Let us know in the comments below! --------------------------------------------------------------------------------------------------------------------------- Follow SI on all social channels! Twitter: https://buff.ly/2Pf9t9e Facebook: https://buff.ly/3l3ziFu Instagram: https://buff.ly/3oZia6i TikTok: https://buff.ly/3wGhuFc Subscribe to SI today for access to the biggest teams, the boldest names, and the legendary stories that only we can deliver: https://buff.ly/34iPNWS