The 21-year-old South Korean, who beat six-times champion Novak Djokovic in the fourth round at Melbourne Park, has climbed from 58th to 29th in the world, the highest ranking achieved by a Korean player.
Bulgarian world number four Grigor Dimitrov faces a race against time to get fit to defend his title in Sofia after shoulder pain and exhaustion prevented him from practising.
(Reporting by Angel Krasimirov, editing by Ed Osmond)
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