"My emotions did get the best of me this past weekend when I disagreed with the umpire," Williams tweeted Wednesday. "It has been a long road to get back to the US Open this year, and I am thankful to have had such a great two weeks in New York."
Williams' tweet came two days after she was cited for a code violation and fined US$2,000 for verbally abusing chair umpire Eva Asderaki.
Facing a break point while serving in the first game of the second set Sunday night, Williams hit a forehand that she celebrated with a yell of "Come on!" Asderaki applied the hindrance rule, noting the scream came while Stosur reached out and got a racket on the ball. Asderaki awarded the point to Stosur.
That set Williams off on a series of insults directed at the official, reminiscent of her tirade on the same court when she berated and brandished her racket at a referee who called a foot fault in the 2009 semifinal against Kim Clijsters.
Stosur stunned Williams 6-2, 6-3 Sunday, winning her first Grand Slam title. She became the first Australian woman to win a major championship since Evonne Goolagong Cawley at Wimbledon in 1980.
Williams won two tournaments heading into the U.S. Open and was considered a favourite despite being sidelined nearly a year with injuries and health issues. She returned in June after dealing with two foot surgeries and blood clots in her lungs.