Naomi Osaka defeated by Amanda Anisimova at Australian Open, Ash Barty through to fourth round

Ash Barty has reached the fourth round of the Australian Open, but defending champion Naomi Osaka has been knocked out of the tournament by unseeded American Amanda Anisimova.

Barty progressed with a 6-2, 6-3 win over Italian 30th seed Camila Giorgi on Rod Laver Arena, with many observers feeling Osaka was certain to be her next opponent in the last 16.

But instead, it will be Anisimova, who scored an upset victory over the four-time major winner, claiming a 4-6, 6-3, 7-6 (10-5) triumph on Margaret Court Arena.

Osaka had two match points when she led 5-4 in the third set, with the 60th-ranked Anisimova serving to stay in the contest.

Anisimova held serve before a super tiebreak was later needed to decide the match. The 20-year-old forced Osaka to play catch-up early, always keeping her nose in front on the scoreboard.

She served for the match at 9-5, with an ace sealing the result and leaving the former world number one's title defence in tatters.

«I thought she [Anisimova] played really well,» Osaka said after the match.

«For me, I thought it was a pretty high-level match. I think the pace of her ball surprised me, but other than that, it was fun to play.»

Anisimova — who has been ranked as high as 21 — and Barty have previously played each other once, with Barty winning their 2019 French Open semi-final in three sets on her way to claiming her first major title.

This is the fourth year in a row that Barty has at least reached this stage of the Australian Open.

She wrapped up her match against Giorgi while Anisimova and Osaka were battling their way through the third set of their encounter.

«I would have loved to have had the opportunity to play Naomi,» Barty said at her post-match media conference. 

«I love to test myself against