Cesar Kist defeated Oscar Bustos 6-4 6-3 in the Brazil 1 Masters 4 round of 16 on clay. The upset overturned the form book — Oscar Bustos came in leading the head-to-head 1–0. Cesar Kist claimed a first win over Oscar Bustos in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1991-05-13 | Brazil 3 Masters 2 | R16 | clay | Oscar Bustos | 6-4 7-6 |