Bulgarian third seed Grigor Dimitrov battled past local favourite Nick Kyrgios 7-6(3) 7-6(4) 4-6 7-6(4) in three hours and 26 minutes to advance to the quarter-finals.
"Believe," Kyrgios told Dimitrov, who is yet to win a grand slam, as the pair met at the net following the match. Dimitrov takes on Briton Kyle Edmund next.
Dimitrov kept his cool in the Rod Laver Arena maelstrom to knock home favourite Kyrgios. Third seed Dimitrov absorbed 76 winners and struck 64 of his own to edge a scintillating duel.
Kyrgios fought until the end, breaking back when Dimitrov served for the match at 5-3 in the fourth set but Dimitrov booked a quarter-final spot in the night's third tiebreak when he fired a sublime forehand winner.
Defeat for Kyrgios means Australia's long wait for a men's champion at their home slam will extend to a 43rd year.
Dimitrov will play British player Kyle Edmund for a place in his second successive semi-final in Melbourne.
