Serena Williams` series of furious vows with the umpire during the US Open final overshadowed the maiden victory of 20-year-old Naomi Osaka. Never had she thought it would backfire as people criticised Serena for her behaviour. Months after the incident, Swiss tennis star Roger Federer kept his views, saying Serena `went too far with her controversial rant`. "I feel like Serena should have walked away. She did, but she went too far. She should have walked earlier," said Federer. Serena received a code violation for coaching, a penalty point for racquet abuse and a game penalty for calling the umpire a liar and a thief during her defeat by Osaka. Nevertheless, the Swiss star did have some sympathy for Serena, adding: "The umpire maybe should not have pushed her there. It`s unfortunate, but an incredible case study." Osaka`s 6-2, 6-4 win over Serena quickly became infamous for the American`s flare-up during the final.