NEW YORK, Aug 24 (Reuters) - Aryna Sabalenka and Novak Djokovic overcame early tests to reach the U.S. Open second round before the Grand Slam descended into chaos late on Sunday when Daniil Medvedev launched a tirade at the match umpire and fans disrupted his opponent's service game.

Aryna Sabalenka launched the defense of her US Open crown with a victory Sunday while Novak Djokovic made a successful start to his latest bid for a record 25th Grand Slam singles title – but a raging Daniil Medvedev exited.

Aryna Sabalenka on Sunday launched the defense of her US Open crown with victory, while Novak Djokovic made a successful start to his latest bid for a record 25th Grand Slam singles title, but a raging Daniil Medvedev exited.