World No. 1 Williams defeated Sharapova 12 months ago to win her sixth Australian Open title as part of a brilliant 2015 season, and Williams proved too much for Camila Giorgi in a 6-4 7-5 win.

MORE: Australian Open winners of the 21st century | Complete list of women’s seeds

Sharapova, champion in 2008, was dominant in a 6-1 6-3 beating of Nao Hibino, while Agnieszka Radwanska and Petra Kvitova beat Christina McHale and Luksika Kumkhum in straight sets.

However, former world No. 1 Caroline Wozniacki was the highest profile of a number of seeds to fall at the first hurdle on Monday, including home favorite Sam Stosur.

Headline acts 

Williams battled a knee injury in the build-up to the first major of 2016, but the 21-time Grand Slam winner remained in relative control against the big-hitting Giorgi — the highest-ranked unseeded player in the draw.

Sharapova was playing her first competitive match of the year but was in ruthless form against Hibino. She had a small blip when serving out for the match at 5-2, but that was the only negative for the impressive Russian.

WTA Finals champion Radwanska contended well with hot temperatures in a classy showing against McHale, while Kvitova defied a stomach bug that had prevented her from playing thus far this season in her win against Kumkhum.

Seeds saying goodbye 

The top players did not have it all their way on day one, though, with seven seeds biting the dust, including Wozniacki.

The 16th seed was outsted in three sets by Yulia Putintseva, marking Wozniacki’s first-ever opening-round loss at Melbourne Park.

It was a similar story for 17th seed Sara Errani, who lost in three to Margarita Gasparyan, while Stosur (25) — who has never gone beyond round four at her home tournament — was sent packing by Karolina Pliskova.

Sloane Stephens (24) and Anna Karolina Schmiedlova (27) also said goodbye.

Stephens lost 6-3 6-3 to Wang Qiang, while Schmiedlova was beaten by the same scoreline by Daria Kasatkina. Anastasia Pavlyuchenkova (26) and Andrea Petkovic (22) are also heading home.

Key stats

Wozniacki has now progressively suffered elimination a stage earlier each year since reaching the semifinals in 2011.

Serena hit 19 winners en route to victory, but the American had particular success at the net by winning all seven points when coming in from the baseline.

Sharapova was guilty of 21 unforced errors against Hibino. On first serve, though, the fifth seed lost just four of 28 points.

Tweets of the Day 

“First win of the season was worth the wait! Happy it came at the @AustralianOpen.” — Petra Kvitova is elated with her winning return after bout of illness.

“First round victory at the Australian Open. Already focused on my next match!” — Carla Suarez Navarro is taking no time to savour her opening round win against Viktorija Golubic.

They said what?

“Oh my god. I was cramping the whole third set! I tried to keep my emotions inside and imagine that I was losing!” — Yulia Putintseva describes how she maintained focus during her victory over Wozniacki.

“A for effort. Yeah A for effort.” — Serena responds when asked to grade the start of the defence of her title.

“I would say it’s a pretty sh–y start to the season.” — Wozniacki is none too pleased with her defeat.

“I’m disappointed that I lost here but if I play until I’m 35, I have plenty more grand slams to go. I just have to look past it.” — Stephens, seeded 24th, is philosophical about her defeat to Qiang Wang.

Next up 

Victoria Azarenka, a two-time winner, has started the season in fine form, with the Brisbane International title to her name already in 2016. The 14th seed is tipped as a contender in Melbourne and starts her campaign against Alison Van Uytvanck on Tuesday.

Second seed Simona Halep has a tricky opener againsst Zhang Shuai, while last year’s Wimbledon finalist Garbine Muguruza plays Anett Kontaveit.

Venus Williams, finalist in 2003, is up against Johanna Konta, and sister Serena is back in action on Wednesday against Hsieh Su-wei.

Sharapova plays Aliaksandra Sasnovich in round two, while Radwanska has a mouth-watering contest against the in-form Eugenie Bouchard.

Results 

Serena Williams (1) beat Camila Giorgi 6-4 7-5 Agnieszka Radwanska (4) beat Christina McHale 6-2 6-3 Maria Sharapova (5) beat Nao Hibino 6-1 6-3 Petra Kvitova (6) beat Luksika Kumkhum 6-3 6-1 Carla Suarez Navarro (10) beat Viktorija Golubic 7-5 6-4 Belinda Bencic (12) beat Alison Riske 6-4 6-3 Roberta Vinci (13) beat Tamira Paszek 6-4 6-2 Yulia Putintseva beat Caroline Wozniacki (16) 1-6 7-6 (7-3) 6-4 Margarita Gasparyan beat Sara Errani (17) 1-6 7-5 6-1 Elizaveta Kulichkova beat Andrea Petkovic (22) 7-5 6-4 Svetlana Kuznetsova (23) beat Daniela Hantuchova 6-0 6-2 Qiang Wang beat Sloane Stephens (24) 6-3 6-3 Karoline Pliskova beat Sam Stosur (25) 6-4 7-6 (8-6) Lauren Davis beat Anastasia Pavlyuchenkova (26) 1-6 6-3 6-4 Daria Kasatkina beat Anna Karolina Schmiedlova (27) 6-3 6-3 Kristina Mladenovic (28) beat Dominika Cibulkova 6-3 6-4 Daria Gavrilova beat Lucie Hradecka 7-6 (7-3) 6-4 Hsieh Su-wei beat Jelena Ostapenko 3-6 7-5 6-1 Magdalena Rybarikova beat Yanina Wickmayer 3-6 6-3 7-5 Kurumi Nara beat Oceane Dodin 7-6 (7-2) 6-2 Maria Sakkari beat Wang Yafan 6-4 1-6 6-3 Nicole Gibbs beat Klara Koukalova 6-2 2-6 6-1  Han Xinyun beat Mariana Duque-Marino 6-2 2-1 (retired) Aliaksandra Sasnovich beat Evgeniya Rodina 6-3 7-6 (7-2) Anna-Lena Friedsam beat Lourdes Dominguez Lino 7-6 (7-3) 2-6 6-1 Monica Niculescu beat Teliana Pereira 6-2 6-1 Kateryna Bondarenko beat Ajla Tomljanovic 7-6 (7-2) 6-3 Eugenie Bouchard beat Aleksandra Krunic 6-3 6-4 Timea Babos beat Heather Watson 6-7 (4-7) 7-5 7-5 Ana Konjuh beat Urszula Radwanska 0-6 6-4 6-3 Irina Falconi beat Anna Tatishvili 6-4 3-6 8-6 Monica Puig beat Magda Linette 6-3 6-0