The defending champion who endured a thrilling five-setter against Tommy Haas in the fourth round, battled past Davydenko 6-4, 3-6, 7-6 (9-7), 7-6 (7-5) in three hours, 13 minutes to set up a semifinal clash with Germany’s Nicolas Kiefer.

21st-seeded Kiefer advanced to his first major semifinal after defeating France’s Sebastien Grosjean 6-3, 0-6, 6-4, 6-7 (1-7), 8-6 in an epic quarterfinal tie.

Meanwhile in the women’s action, second-seeded Kim Clijsters ended Martina Hingis’ spectacular run in Melbourne as she ousted the Swiss returning star 6-3, 2-6, 6-4.

The reigning US Open champion seemed to be on her way to an easy victory when she broke Hingis’ first service game to love and captured the first set, but the Belgian was tested when Hingis secured the second set.

Clijsters finally regained control as she grabbed the decider and claimed a semifinal spot against third-seeded Amelie Mauresmo, who breezed past seventh-seeded Patty Schnyder in straight sets.