Ryuso Tsujino defeated Mark Nielsen 6-0 6-1 in the USA 2 Masters 2 qualifying round on clay. The upset overturned the form book — Mark Nielsen came in leading the head-to-head 2–0. Ryuso Tsujino claimed a first win over Mark Nielsen in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2001-05-14 | Japan F4 | R16 | hard | Mark Nielsen | 6-3 6-3 |
| 1999-06-07 | Japan 1 Masters 1 | QF | hard | Mark Nielsen | 6-2 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.