Melbourne - Last year's Australian Open runner-up Marin Cilic wasted little time in reaching the second round on Monday with a 6-2, 6-4, 7-6 (7/3) win over Australian Bernard Tomic.
Sixth seed Cilic, who lost an epic final in five sets to Roger Federer a year ago, took a shade over two hours to progress on Margaret Court Arena.
The former US Open champion, who led Croatia to a Davis Cup trophy in November, skipped the warm-up Maharashtra ATP tournament with a stiff knee, but showed no signs of the injury against Tomic.
The 30-year-old's victory set up a second-round clash with American Mackenzie McDonald.
Stefanos Tsitsipas (GRE x14) bt Matteo Berrettini (ITA) 6-7 (3/7), 6-4, 6-3, 7-6 (7/4)
Reilly Opelka (USA) bt John Isner (USA x9) 7-6 (7/4), 7-6 (8/6), 6-7 (4/7), 7-6 (7/5)
Yulia Putintseva (KAZ) bt Barbora Zahlavova Strycova (CZE x32) 6-4, 7-6 (7/1)
Lesya Tsurenko (UKR x24) bt Ekaterina Alexandrova (RUS) 6-4, 7-6 (7/4)