Donavan September defeated Mike Mather 6-2 6-1 in the USA 3 Masters 1 round of 64 on hard. The upset overturned the form book — Mike Mather came in leading the head-to-head 1–0. Donavan September claimed a first win over Mike Mather in two meetings, narrowing the head-to-head to 1–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1998-09-11 | USA 3 Masters 2 | R32 | hard | Mike Mather | 6-2 6-2 |