Yunseong Chung defeated Seong Gook Oh 6-2 6-2 in the Korea F4 round of 16 on hard. The upset overturned the form book — Seong Gook Oh came in leading the head-to-head 1–0, but Yunseong Chung had been the form player, winning 2 of their last 4 on hard. Yunseong Chung claimed a first win over Seong Gook Oh in two meetings, levelling the head-to-head at 1–1.
Chung Y. took it in straight sets.
Yunseong Chung beat Seong Gook Oh 6-2 6-2. Umpiry, "Yunseong Chung vs Seong Gook Oh — Korea F4 Round of 16", https://umpiry.com/match/2017-06-19/chung-vs-oh-korea-f4-r16?utm_source=cite (as of 19 June 2017).