Coco Gauff, the 15-year-old tennis prodigy who shot to stardom at Wimbledon last year, has stunned the defending Australian Open champion Naomi Osaka in the third round of the competition. The teenager is through to last 16 of the tournament after she saw off the Japanese champion in two rounds. It’s a clear sign of her incredible progress—she won just three games against Osaka when they met at the U.S. Open last summer. She was in disbelief following the victory, saying: “Two years ago, I lost first-round in juniors, and now I’m here. This is crazy. I was just telling myself one point at a time and keep fighting because you never know what happens on this court. I’m on Rod Laver Arena, I can’t believe this.” The Guardian reports Gauff is the youngest player to beat a top-five-ranked opponent since Jennifer Capriati beat Gabriela Sabatini at the 1991 U.S. Open. Meanwhile, Serena Williams was stunned by China's Qiang Wang—her exit marks the first time she’s not managed to advance past the third round at the Australian Open since 2006.