Athina Briegel defeated Maaike Koutstaal 7-5 6-3 in the Estoril 10K round of 32 on carpet. The upset overturned the form book — Maaike Koutstaal came in leading the head-to-head 1–0. Athina Briegel claimed a first win over Maaike Koutstaal in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1998-01-20 | Bastad 10K | R16 | hard | Maaike Koutstaal | 6-2 0-6 6-2 |