By Eliza Mackintosh, CNN

(CNN) -- Speaking about Saturday's controversial US Open final, Billie Jean King, the tennis legend and equal rights advocate, told CNN's Christiane Amanpour that Serena Williams was "out of line," but umpire Carlos Ramos aggravated the situation.

"Serena was out of line, there's no question, no one's saying she was a good sport," King said. "The point is he [Ramos] aggravated the situation."

What was supposed to be a fairy-tale matchup for Japan's Naomi Osaka and the player she idolizes spun out of control Saturday after Williams was handed code violations that she described as unfair.

It started when chair umpire Carlos Ramos warned Williams for receiving coaching, and eventually ended up with accusations of sexism in the aftermath. Williams, furious over the first call, approached the net and told Ramos: "I don't cheat. I'd rather lose." The match unraveled after that.

"I felt like at the very beginning he blew it," King said. "As an umpire you're supposed to keep the flow of the match going and he did just the opposite."

While King said that Serena Williams was "out of line" for her subsequent behavior -- which included cracking her racket and calling Ramos "a thief" -- she emphasized that Ramos didn't control the match.

King suggested that "everything would have been different" if Ramos had told Williams he wasn't attacking her character from the outset.

Asked about whether sexism played a role in the match, King said that it was still an issue in the world of tennis.

"Men are outspoken when they stand up for themselves. And women are looked at as hysterical," King said. "We are not. We are also speaking up." King had tweeted a similar statement after the match, thanking Williams for calling out the double standard.

King said that moving forward, the game has to change, suggesting that coaching should be allowed and umpires need to communicate calls better.

"Out of crisis creates opportunity," King said. "This is an opportunity for us to get it right."

And on the future of the sport, King said she's looking forward to seeing more of Osaka.

"She's going to be a superstar and she already is, but now it's just the beginning," King said. "There should be no asterisk, she won fair and square. She was definitely playing better than Serena from the get-go, so this is hers and hers 100% no matter what was happening with the chaos."