Osaka tested but into second round in Melbourne

Tennis - Australian Open - First Round - Melbourne Park, Melbourne, Australia - January 20, 2020 Japan's Naomi Osaka celebrates winning the match against Czech Republic's Marie Bouzkova REUTERS/Kai Pfaffenbach

MELBOURNE (Reuters) - Defending champion Naomi Osaka overcame a patchy and error-prone performance to advance to the second round of the Australian Open on Monday with a 6-2 6-4 victory over Czech Marie Bouzkova.

The 22-year-old Japanese next faces China's Zheng Saisai, who needed just 72 minutes to beat Russian qualifier Anna Kalinskaya 6-3 6-2.