Milos Raonic suffered a shock first-round loss at the Australian Open on Tuesday, marking his earliest exit in Melbourne.

The Canadian, a semi-finalist at the year's opening grand slam in 2016, was stunned by Lukas Lacko 6-7 (5-7) 7-5 6-4 7-6 (7-4).

World number 23 Raonic underwent wrist surgery last year, but he has been a regular contender at Melbourne Park.

However, his loss to Lacko marked the first time he has suffered a first-round Australian Open loss.

It was also his earliest grand slam exit since the 2011 French Open.

Raonic served 36 aces against Lacko, but he was unable to stop the Slovakian world number 86.

Lacko hit 65 winners on his way to closing out a victory in three hours, 23 minutes.