Wojtek Kowalski defeated Christian Schaffkes 6-2 6-1 in the Netherlands Masters 4 round of 16 on clay. The upset overturned the form book — Christian Schaffkes came in leading the head-to-head 1–0. Wojtek Kowalski claimed a first win over Christian Schaffkes in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1991-06-24 | Netherlands Masters 3 | QF | clay | Christian Schaffkes | 7-6 6-3 |