Veteran Samantha Stosur won't let her fifth successive Australian Open first round loss force her into retirement, confirming she's planning to return in 2021.

Thirteen Australians hit the courts at the Australian Open on Tuesday as the tournament plays catch-up after Monday's rain.

Novak Djokovic has opened his Australian Open title defence with a testing four-set win over German Jan-Lennard Struff.

Greek Stefanos Tsitsipas had far too much firepower for Italian Salvatore Caruso, easing to a straight-sets win in his opening match at the Australian Open.