Cilic took down Denis Istomin of Uzbekistan 6-0, 6-4 to advance to the quarterfinals of the event, which is considered a tuneup for the upcoming Australian Open.
Another Croatian, 6-foot-10 Ivo Karlovic, the No. 4 seed, rolled over Ivo Minar of the Czech Republic 6-1, 6-4.
Fifth-seeded Rainer Schuettler of Germany beat countryman Simon Gruel 6-4, 6-2, No. 7 Janko Tipsarevic of Serbia outplayed Israeli Dudi Sela 7-6, (7-3), 6-4 and No. 8 Marcel Granollers of Spain topped German Andreas Beck 6-4, 6-1.
Indian wild card Somdev Dewarman upset sixth-seeded Carlos Moya of Spain 4-6, 7-5, 6-4 . Moya won the tournament in 2004 and 2005.
The Australian Open starts Jan. 19 in Melbourne.