Top seed Bernard Tomic started his quest to win a second Sydney International title by outclassing fellow Australian Jordan Thompson in the second round on Wednesday.
Tomic made an encouraging start to 2016 when he reached the semi-finals of the Brisbane International last week and coasted into the last eight in Sydney by beating Thompson 6-2 6-2.
The world number 17, who was given a first-round bye, needed only 49 minutes to get the better of Thompson as the outsider saved only one of the five break points he faced.
Tomic, champion in Sydney three years ago, lost just seven points on his serve in a one-sided match to set up a quarter-final against Teymuraz Gabashvili.
Second seed Dominic Thiem retired after being troubled by blisters during his match against Gilles Muller.
The world number 20 from Austria lost a first-set tie-break and was level at 2-2 in the second when he decided he could not continue.
Defending champion Viktor Troicki looked capable of retaining his title as he made light work of beating Tommy Robredo 6-1 6-4.
Grigor Dimitrov went through courtesy of a 7-6 (7-2) 6-4 win over Pablo Cuevas, but fifth seed Andreas Seppi crashed out with a 6-3 1-6 6-3 defeat at the hands of qualifier Nicolas Mahut.
Jeremy Chardy and Alexandr Dolgopolov are also through, while Gabashvili saw off Federico Delbonis 6-3 6-3.