SIX-time champion Novak Djokovic was stunned in straight sets by Hyeon Chung only hours after Tennys Sandgren beat No 5 Dominic Thiem at the Australian Open.

The back-to-back upsets today have set up a very unexpected quarter-final: Chung, the first Korean to reach the last eight at a grand slam, versus 97th-ranked Sandgren, who had never won a match at a major or beaten a top-10 player until last week.

No 58-ranked Chung relentlessly attacked Djokovic — who is playing his first tournament since Wimbledon last July because of an injured right elbow — in the 7-6 (7/4) 7-5 7-6 (7/3) fourth-round win.