Chung Hyeon beat Pablo Cuevas 61 63 in the fourth round of the ATP Indian Wells Masters.
Cuevas fended off nine match points before eventually losing in the first-ever meeting between the pair.
Chung advanced to the quarter-finals, where he will play either world number one Roger Federer or France's Jeremy Chardy.
Down a set and behind 5-0 in the second set, Cuevas miraculously saved seven match points to win the game.
He then served out the next game to cut Chung's lead to 5-2 and then broke the South Korean in the game after that.
Cuevas saved two more match points in the ninth game but his luck finally ran out.
Chung will face Federer for the second time this year in the next round. Chung made a Grand Slam breakthrough when he reached the semi-finals of the Australian Open in January but had to retire in his match with Federer because of a foot blister.
