Defending champion Naomi Osaka overcame a tantrum and progressed to the third round after beating China's Saisai Zheng in straight sets 6-2, 6-4 on Margaret Court Arena. In a match that lasted one hour and 20 minutes, Osaka took the first set after securing a crucial break in the sixth game to go 4-2 up before doing the same again at 5-2. Zheng fought back in the second and broke the Osaka serve in games 3 and 5. Nevertheless the No. 3 seed regained her composure by winning four games in a row at 4-2 down as the outgunned Zheng double-faulted on match point. She will next meet 15-year-old Coco Gauff for a place in the fourth round, having met the American at the same stage of the US Open. Osaka won that showdown 6-3 6-0 against Gauff, who beat Sorana Cirstea 4-6 6-3 7-5. The match had echoes of Osaka's tempestuous third-round win over Hsieh Su-wei at the same venue last year when Osaka was driven to distraction by her opponent's unorthodox game of drop-shots and slices. Osaka ultimately came back from a set down to overhaul Hsieh and went on to claim her second Grand Slam title with another stormy victory over Petra Kvitova. "Yeah, it's really tough, because you start thinking she's not hitting winners," said Osaka, who was desperate to avoid a third set against the 42nd-ranked Zheng. "You're the one making all the errors. And you try to tell yourself not to make that many errors, but you have to go for those balls. "So it's like you're walking a very fine line between being very aggressive or attempting to push but that's her game. So it's very hard."