Geraldine Aizenberg defeated Mariana Mesa 6-2 6-3 in the San Juan 10K round of 32 on clay. The upset overturned the form book — Mariana Mesa came in leading the head-to-head 1–0, but Geraldine Aizenberg had been the form player, winning 6 of their last 8 on clay. Geraldine Aizenberg claimed a first win over Mariana Mesa in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-09-20 | Asuncion 10K | QF | clay | Mariana Mesa | 6-4 3-6 7-6 |