World number two Rafael Nadal began his bid for a men's record 21st Grand Slam title with a straight-set victory over Laslo Djere at the Australian Open.

The Spaniard did not play in the ATP Cup last week after struggling with a back injury, but he moved well in a 6-3 6-4 6-1 victory over the Serb.

He will play Viktor Troicki or Michael Mmoh in the second round.

Russian fourth seed Daniil Medvedev and compatriot Andrey Rublev also advanced on the second day at Melbourne Park.

However, 13th seed David Goffin squandered four match points as he was stunned in five sets by Australian wildcard Alexei Popyrin.

Popyrin, who was one of the 72 players to undergo 'hard' quarantine before the Grand Slam began, fought back to beat the Belgian 3-6 6-4 6-7 (4-7) 7-6 (8-6) 6-3.

Nadal, who reached the final in Melbourne in 2019, did not have to exert himself too much in his win over Djere.

His only troubles came when serving for the set - he was broken to love at 5-2 in the first and was forced to stave off break point at 5-4 in the second.

Meanwhile, Medvedev extended his winning streak to 15 matches with a 6-2 6-2 6-4 win over Canada's Vasek Pospisil.

Eighth seed Rublev beat Yannick Hanfmann of Germany 6-3 6-4 6-4 to continue his own good form.

Russia's Karen Khachanov overcame a second-set dip to beat Australian Aleksandar Vukic 6-3 6-7 (4-7) 7-6 (7-2) 6-4.