Agnieszka Radwanska suffered a stunning early exit at the hands of Mirjana Lucic-Baroni on a day of major shocks at the Australian Open.

Radwanska has been to the semi-finals in Melbourne in two of the last three years, but bowed out in the second round on this occasion, Lucic-Baroni wrapping up a straight-sets win in just over an hour, after Novak Djokovic's shock defeat to Denis Istomin.

While Radwanska crashed out there were no such difficulties for 22-time grand slam champion Serena Williams, a victor in a repeat of the 2015 French Open final against Lucie Safarova.

And it was largely business as usual for the other seeds in the draw, as Karolina Pliskova, Dominika Cibulkova and Johanna Konta all came through in straight sets.

AGONY FOR AGA

Lucic-Baroni went 0-2 against Radwanska in their previous two meetings on the WTA Tour and went into Thursday's contest having never progressed beyond the second round of the Australian Open.

But the 34-year-old Croatian played like she had nothing to lose to emphatically end Radwanska's hopes of a first grand slam title for at least another few months.

Radwanska was unable to live with the positive approach of Lucic-Baroni, who hit 20 unforced errors but struck 33 winners to the Pole's eight to seal a hugely impressive 6-3 6-2 success.

WILLIAMS NOT EXPECTING SERENE ROUTE TO FINAL

Williams could have hardly have asked for a tougher start to her campaign, having been pitted against two former top-10 players in Belinda Bencic and now Safarova.

However, she has dealt with those challenges in supreme fashion and has yet to drop a set after her 6-3 6-4 triumph over the Czech, who had saved nine match points in a first-round thriller against Yanina Wickmayer.

Next up for the American is compatriot Nicole Gibbs, ranked 90 places below her.

Yet Williams is taking nothing for granted, saying on court afterwards: "That's a great way to start to the tournament [beating two former top-10s], it's not going to get any easier."

OVA IN THE BLINK OF AN EYE

Karolina Pliskova is regarded as one of the biggest threats to a potential repeat of a final between Angelique Kerber and Williams, and she showed just why in her demolition of 18-year-old Anna Blinkova.

Fifth seed Pliskova needed only 59 minutes to cruise to a 6-0 6-2 victory, dominating in every facet to set up a third-round clash with Jelena Ostapenko, who knocked out 31st seed Yulia Putintseva.

Alize Cornet (28), was another seed to exit the tournament early, the Frenchwoman beaten in three sets by Greece's Maria Sakkari, who now faces Lucic-Baroni.

But Cibukova saw off Hsieh Su-wei 6-4 7-6 (10-8) and Konta defeated Naomi Osaka 6-4 6-2, while 12th seed Timea Bacsinsky and former world number one Caroline Wozniacki - seeded 17th - enjoyed straight sets wins over Danka Kovinic and Donna Vekic respectively.