Marta Kostyuk earns glowing praise from Serena Williams – but not for her tennis: "I really like when she does backflips”

Marta Kostyuk is not just making an impact in the singles at the Cincinnati Open, but also the doubles. The Ukrainian was half of a doubles pairing that dumped out Serena and Venus Williams on the sisters first match together in four years. The 23-time Grand Slam champion was glowing with praise for...