Alex de Minaur continues to warm-up for the Australian Open with a hard-earned straight sets win in his Sydney International opener on Monday.

The Australian No.1 was made to work hard by Serbian world No.45 Dusan Lajovic in both sets before finishing strongly to claim a 6-4 6-3 win on Ken Rosewall Arena.

De Minaur, who rose to world No.29 on Monday, made the final last year and will aim to go one better after defending champion Daniil Medvedev withdrew from his title defence.

Medvedev, who lost to Kei Nishikori in the Brisbane final on Sunday, had beaten de Minaur in last year’s final and was slated to meet the Sydney product in the quarter-final this week.

The 19-year-old de Minaur, who had to wait three hours to play due to rain delays, will now meet American qualifier Reilly Opelka or Albert Ramos-Vinolas from Spain in the second round.

Medvedev’s pull-out comes hours after defending women’s champion Karolina Pliskova also withdrew following her triumph over Lesia Tsurenko in Brisbane.

Tsurenko was also a last-minute withdrawal.

Greek world No.15 Stefanos Tsitsipas is the favourite to take out the men’s title.