WTA Finals: Sloane Stephens beats Naomi Osaka in battle of US Open champions

American comes out on top in three sets, 7-5, 4-6, 6-1 Both players are making debuts in season-ending tournament Sloane Stephens came out on top in a match between the two most recent US Open champions. The 2017 champion beat Naomi Osaka 7-5, 4-6, 6-1 on Monday at the WTA Finals, the season-ending tournament for the top eight players in the world. Both players are making their debut appearances at the tournament, but Stephens was more composed while Osaka, who became the first Japanese player t...