Guillaume Marx defeated Andreas Lesch 7-6 4-6 7-6 in the Switzerland Masters 3 round of 32 on carpet. The upset overturned the form book — Andreas Lesch came in leading the head-to-head 1–0. Guillaume Marx claimed a first win over Andreas Lesch in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1991-10-28 | Switzerland Masters 1 | R16 | hard | Andreas Lesch | 6-4 6-3 |