Melbourne, Jan 22 (IANS): World No.1 Iga Swiatek's hopes of a second straight hard-court major are over following a crushing defeat to Wimbledon champion Elena Rybakina in the Australian Open fourth round.

Round of 16 showdowns did not come any bigger than two reigning Grand Slam champions at this stage, reports AusOpen.

After the Pole's benchmark-setting feats of 2022, the 23-year-old Rybakina served a reminder she is in the box seat to further shake up the top order this season with her 6-4 6-4 triumph.

The two women shared the major spoils since Australian Open champion Ash Barty's retirement last year and on Sunday, they met for just the second time, following Swiatek's straight-sets victory indoors in Ostrava in 2021.

Neither placed too much weight on that previous encounter, given the heights both have scaled since.

A runaway world No.1 last season, thanks largely to her Roland Garros and US Open successes, Swiatek had barely raised a sweat against qualifier Cristina Bucsa in the previous round, but she was yet to really hit her straps as she bid to better her semifinal run at Melbourne Park last year.

That campaign ended to the heavy-hitting Danielle Collins, incidentally the player Rybakina had outlasted in three sets to reach the fourth round here for the first time on Friday.

It was an inauspicious beginning before the first ball was even struck on Rod Laver Arena when Swiatek was handed a code violation warning for taking too long.

It set the tone for a slow start to proceedings as she subsequently dropped her opening service game.

The top seed soon managed to settle, but she was not having it all her own way.

Rybakina is among a select group who possess the sheer force capable of pushing the Pole around the court and she found tremendous success clobbering hard and flat into her opponent's forehand.

The Kazakh's third ace capped a statement start as she sealed the opening set after 42 minutes.

Struggling with the depth and pace of shot headed her way, Swiatek needed to orchestrate quite the turnaround if she was to survive this onslaught.

She had done so from a set down in her past three Grand Slam fourth rounds and raised her intensity immediately at the beginning of the second set, adding greater sting to her forehands to jump to 3-0 at the one-hour mark.

It was an all-too-fleeting swing in momentum.

No sooner was Swiatek in the driver's seat than she again found it exceedingly difficult to drag her heavy-striking opponent out of her hitting zone.

Rybakina had reimposed her authority, and with a break again in hand, she advanced to her maiden Australian Open quarterfinal with a sixth ace and seventh forehand winner in succession.

The 22nd seed has now reached the quarterfinals at three of the four majors, having first done so at Roland Garros in 2021, where she defeated Serena Williams.

She next faces former Roland Garros champion Jelena Ostapenko for a semifinal berth, an opponent she has not found success against in two prior meetings.