Matias Oneille defeated Mariano Campos 6-1 6-4 in the Argentina F5 round of 32 on clay. The upset overturned the form book — Mariano Campos came in leading the head-to-head 1–0, but Matias Oneille had been the form player, winning 3 of their last 7 on clay. Matias Oneille claimed a first win over Mariano Campos in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-05-29 | Argentina 1 Masters 3 | QF | clay | Mariano Campos | 7-5 6-2 |