Australian Open 2020: The major happenings on Day 4

Sania made a winning return to tennis after a maternity leave by winning the Hobart International women's doubles title recently.

However, her joy was cut short in the first round of the Australian Open.

Sania and her Ukrainian partner Nadiia Kichenok were trailing 2-6, 0-1 against Xinyun Han and Lin Zhu when the Indian ace called it quits due to a calf injury.

Thiem overcame wildcard Alex Bolt in a five-set thriller.

The two-time French Open finalist beat world number 140 Bolt 6-2, 5-7, 6-7 (5-7), 6-1, 6-2 in Melbourne.

He took three hours and 26 minutes to outlast his opponent.

"It was great fun for both of us - it's really nice to play under such an atmosphere," Thiem said.

Russia's Medvedev reached the third round with a straight-set win over Spanish qualifier Pedro Martinez.

The 23-year-old, who reached the US Open 2019 final, had a nosebleed in the second set.

However, he sealed the tie 7-5, 6-1, 6-3 in just over two hours.

Germany's Zverev beat Belarusian Egor Gerasimov 7-6 (7-5), 6-4, 7-5.

Bencic overcame Jeļena Ostapenko in a tight 7-5, 7-5 battle.

Second seed Pliskova beat Laura Siegemund in a 6-3, 6-3 battle to advance.

Vekic, who beat Maria Sharapova earlier, trumped Alize Corent 6-4, 6-2 in straight sets.

Meanwhile, Garbine Muguruza went on to overcome Ajla Tomljanović 6-3, 3-6, 6-3.

17th seed Angelique Kerber tamed Aussie wildcard Priscilla Hon 6-3, 6-2.