Teenager Coco Gauff delivered an upset once again by defeating the defending champion Naomi Osaka in straight sets. The American will now advance to the second week and fourth round of the Australian Open.

In an intense encounter, the 15-year-old took advantage of the errors made by her opponent to win 6-3 6-4, reaching the fourth round of a Slam for only the second time in her career.

Osaka excelled in the pairs only previous meeting at last year's U.S Open, but it was Gauff who was victorious this time in her debut appearance at the Australian Open.

Stunned by her victory, Gauff said: "Two years ago I lost the first round in juniors, 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," she added.

"I'm on Rod Laver Arena, I can't believe this."

Gauff will face either China's Zhang Shaui or American Sofia Kenin in the fourth round.

Following the defeat, Osaka explained it was a night where "nothing went right" for her.

“I love her, but I don’t like this feeling of losing to her. I feel bad for my entire team. We came here to win the tournament and I’m sort of like the vessel that everyone’s hard work goes into and I let everyone down.

“Also my mum and dad are here this week, so that makes it hurt a little bit more,” the defending champion explained.

So far, the tournament has seen shock exits from tennis sensation Serena Williams and now the world number three Osaka.