The fifth day at the Australian Open proved to be one full of upsets. After Qiang Wang beat Serena Williams, Coco Gauff continued her stellar run by upsetting defending champion Naomi Osaka 6-3, 6-4 in the third round.

In doing so, Gauff, 15, became the youngest player to defeat a top-five opponent in a women's tour-level match.

One of the biggest themes throughout the match was Osaka making unforced errors, which put her into big holes. She committed 30 unforced errors while Gauff had just 17. 

These two faced off in the third round of the U.S. Open last September, but Osaka got the best of the 15-year old with a victory.

"Her serve is way better," Osaka told ESPN after Friday's match. "I feel like I wasn't really swinging freely, and she was."

Gauff became the first American-born tennis player in 30 years to reach the third round in her first three major appearances. The Australian Open has certainly been an impressive showing for Gauff, as she defeated Venus Williams earlier this week.

With the upset win over Osaka, Gauff will face off against No. 14 seed Sofia Kenin, who also young at just 21 years old. Kenin beat Zhang Shuai 7-5, 7-6 (7) to reach the fourth round, which takes place on Saturday.

With wins over Williams and now Osaka under her belt, the sky is the limit in terms of what Gauff can accomplish in the Australian Open and beyond.