Ji Sung Nam defeated Ji Hoon Son 6-1 6-2 in the Vietnam F3 semi-final on hard. The upset overturned the form book — Ji Hoon Son came in leading the head-to-head 2–0, but Ji Sung Nam had been the form player, winning 8 of their last 9 on hard. Ji Sung Nam claimed a first win over Ji Hoon Son in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2018-02-05 | Turkey F5 | R32 | clay | Ji Hoon Son | 4-6 7-6(3) 6-1 |
| 2013-05-06 | Korea F2 | R32 | hard | Ji Hoon Son | 6-7(3) 6-3 6-3 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.