Nick Kyrgios overcame an impressive comeback to beat Karen Khachanov 6-2 7-6(5) 6-7(6) 6-7(7) 7-6(8) to progress to the last-16 stage of the Australian Open. The 24-year-old put in another box-office performance, producing an array of forehands, smashes and tweeners, to see off world number 17 after a titanic struggle. The Australian, whose best showing at his home Grand Slam was a quarter-final appearance in 2015, was coasting in the first set – leading 5-2 – when he had to call for the trainer. Some treatment seemed to arrest an apparent hamstring strain but sets two and three were far tighter affairs, with Kyrgios and Khachanov sharing a tiebreak each to send the match to a fourth set. The firebrand Australian had an altercation with the umpire in the fourth set – whereby he asked the chairperson "what are you stupid?" – and would again lose that stanza on a tiebreak. A fourth set in succession would settle the match and on his third match point of the match the Australian progressed after four hours and 26 minutes.