Although September is Djokovic's third-most successful month of the year, he has the most variety of tournament wins there. He's won 12 titles in all, including four US Opens, six ATP 500s in Beijing, one ATP 500 in Tokyo—and even one ATP Masters 1000 Rome, during COVID-19.

MIAMI — After two decades of professional tennis, 99 career singles titles and 24 Grand Slam triumphs, Novak Djokovic has become a mystery — to tennis fans and to himself. Both parties are ...