Simona Halep recovered from the brink of defeat to overcome Australian Alja Tomljanovic in a deciding set ©Getty Images

Simona Halep won five straight games in the deciding set to recover from the brink of defeat and overcome Australian Alja Tomljanovic as the second round of the Australian Open got underway at Melbourne Park.

The Romanian second seed looked like being the highest-profile casualty so far at the year’s first Grand Slam with her opponent Tomljanovic serving for a famous win on home soil.

However, Halep broke serve to begin a run of five straight games won and prevail 4-6 6-4 7-5 on the Margaret Court Arena.

Despite Halep holding on for victory, two of the top ten women’s seeds were not so lucky and suffered surprise defeats.

The first match of the day on the Rod Laver Arena saw eighth seed Bianca Andreescu of Canada comprehensively beaten 6-2 6-3 by Su-wei Hsieh of Taiwan.

Ninth seed Petra Kvitova of the Czech Republic was also a casualty as she lost 6-4 1-6 6-1 to Romania’s Sorana Cirstea.

Three of the top ten women’s seeds enjoyed comfortable passages through to round three including Japan’s Naomi Osaka, the third seed, who beat Caroline Garcia of France 6-2 6-3.

Seventh seed Aryna Sabalenka of Belarus was also a straight sets winner as she defeated Daria Kasatkina of Russia 7-6 6-3.

Men's top seed Novak Djokovic was made to battle for his third round place after he was taken to four sets by Frances Tiafoe ©Getty Images
Men's top seed Novak Djokovic was made to battle for his third round place after he was taken to four sets by Frances Tiafoe ©Getty Images

Tenth seed Serena Williams continued her serene progress in the tournament, with the American dropping just three games on the way to a 6-3 6-0 win against Nina Stojanovic of Serbia.

Serena’s sister Venus suffered a twisted ankle during her match against Sara Errani and battled on despite being in pain, with the Italian running out an emphatic winner 6-1 6-0.

In the men’s draw, top seed Novak Djokovic was tested on Rod Laver Arena needing four sets to overcome Frances Tiafoe of the United States 6-3 6-7 7-6 6-3.

All the top ten players in action enjoyed victory with Austrian Dominic Thiem, the third seed, overcoming Germany’s Dominik Koepfer 6-4 6-0 6-2.

Sixth seed Alex Zverev of Germany was also a straight sets winner triumphing 7-5 6-4 6-3 against American qualifier Maxime Cressy, while eighth seed Diego Schwartzman of Argentina dropped just five games as he thrashed lucky loser Alexandre Muller of France 6-2 6-0 6-3.

Elsewhere in the men’s draw two seeded players were defeated in five-set thrillers on the John Cain Arena.

The first came in the day session when 17th seed Stan Wawrinka of Switzerland was beaten by 11 points to nine in a final set tie break by Marton Fucsovics, with the Hungarian winning by a final scoreline of 7-5 6-1 4-6 2-6 7-6.

The second came when 29th seed Ugo Humbert of France was beaten by Australian Nick Kyrgios, who was supported by a raucous and partisan night-time crowd as he came from behind to triumph 5-7 6-4 3-6 7-6 6-4.