The best tennis players in the world, like athletes in other sports, can make incredible amounts of money. While they make their money by winning their matches in tournaments, many times more money is earned through endorsement power and commercials.
Alexander Zverev stunned world number one Novak Djokovic in straight sets to win the season-ending ATP Finals and earn the biggest victory of his career.
Britain's Jamie Murray and Brazilian partner Bruno Soares have clinched their place in the ATP Finals doubles semi-finals for the third straight year.
World number one Novak Djokovic underlined why he is favourite to win the ATP Finals with a commanding win over John Isner in their group opener.
Kevin Anderson made a winning debut at the ATP Finals with a 6-3, 7-6(10) victory over Austrian Dominic Thiem in the opening singles match at the O2 Arena on Sunday.