Kyle Edmund beat Hyeon Chung 7-6 (7/3) 5-7 6-4 to reach the quarter-finals of the Brisbane International on Thursday.
The British number two took the first set in a tie-break and withstood a second-set wobble to eventually see off the South Korean.
Edmund will face defending champion Grigor Dimitrov for a place in the last four after the number one seed came through a tough test against John Millman.
The Australian wildcard won the opening set before Dimitrov took the next on a tie-break. The Bulgarian world number three, who saved two match points in the second-set tie-break, then clinched the decider to win 4-6 7-6 (10/8) 6-3.
Elsewhere, American Ryan Harrison came through his second-round match against Yannick Hanfmann.
Harrison dropped the first set against the German, but fought back to win 6-7 (5/7) 6-4 6-2.
He will face Denis Istomin, who earlier saw off American Jared Donaldson 7-6 (7/5) 6-2, in their last-16 clash.