Keys joins the ranks of American greats who have triumphed at the Australian Open.
He scored the winner at the Santiago Bernabeu on Sunday as Madrid beat Barcelona.
The Serbian earned a 7-6(1) 6-3 7-5 victory over fourth seed Casper Ruud in the final match of the 2023 competition.
He last played an official tournament in October and underwent surgery in January.
Djokovic crushed the Grand Slam dream of Greek trailblazer Stefanos Tsitsipas in the one-sided final match by winning 6-3 7-6(4) 7-6(5), a rematch of the 2021 French Open decider.
Clamouring for Russia not to compete at the summer and winter Olympics, President Volodymyr Zelensky said “any neutral flag of Russian athletes is stained by blood.”
The Belarusian soon hit her stride, however, and powered past the American to close out the match and stay unbeaten in six matches this year.
His gloomy expression told the story, though, and he declined to retrieve a drop-shot in the next game, shaking his head at his worried entourage.
Tennis Australia on Tuesday banned the display of Russian and Belarusian flags at the Australian Open following an incident on day one of the tournament.
Scorching heat halted outdoor matches and sent fans scurrying for shade at the Australian Open on Tuesday as players were given an early test of their endurance on a sweltering day two at Melbourne
