Helge Koll defeated Rafael De Mesa 7-5 6-1 in the USA F12 qualifying round on hard. The upset overturned the form book — Rafael De Mesa came in leading the head-to-head 1–0. Helge Koll claimed a first win over Rafael De Mesa in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-03-26 | USA 1 Masters 4 | R32 | hard | Rafael De Mesa | 6-4 6-2 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.