Natalia Gussoni defeated Geraldine Aizenberg 6-1 7-5 in the Santiago 10K round of 16 on clay. The upset overturned the form book — Geraldine Aizenberg came in leading the head-to-head 1–0. Natalia Gussoni claimed a first win over Geraldine Aizenberg in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-09-20 | Asuncion 10K | R32 | clay | Geraldine Aizenberg | 6-3 7-5 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.