Hyeong Keun Song defeated Mark Nielsen 6-2 2-6 6-3 in the Korea Rep F1 round of 32 on clay. The upset overturned the form book — Mark Nielsen came in leading the head-to-head 1–0. Hyeong Keun Song claimed a first win over Mark Nielsen in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-04-02 | Davis Cup G1 SF: NZL vs KOR | RR | hard | Mark Nielsen | 6-3 3-6 6-3 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.