Roger Federer and Serena Williams will be expected to maintain their flawless progress.
Nadal loses his first set at the French Open since 2015 but that blip did not prevent him from marching into the semi-finals.
Kohlschreiber upset second seed Cilic 6-4 6-4 to advance to the BNP fourth round.
Federer powered home to beat Marin Cilic in five sets to win his sixth Australian Open and 20th Grand Slam title.
Federer finished the year at number two in the world, having started at 16, and a season-leading seven titles.