Samantha Stosur tells the Guardian that staying calm during Serena’s outburst at umpire Eva Asderaki in the U.S. Open final wasn’t easy. Stosur went on to win her first Grand Slam title in straight sets.

"I tried to stay cool but it's not easy when 20,000 people are staring down at the court," Stosur said. "And when the two other people you're sharing that court with are involved in such a tense exchange it becomes difficult."

Facing a break point at the start of the second set, Serena powered a forehand and yelled "Come on!" before Stosur had a chance to strike the ball. The chair umpire awarded the point to Stosur, and Williams lost her cool, saying to Asderaki that "You're a hater, and you're just unattractive inside," among other things.

Stosur admitted she heard Williams' scream "Come on!"

"Absolutely," she said. "I was just trying to get the ball back; but Serena did something you can't do…Well, I know it was not directed at me. The umpire got all of it—which probably makes me feel better… You don't expect anyone to say that to an umpire. I certainly wouldn't want to be on the other end of it. It definitely wasn't nice."