Atsuo Ogawa defeated Mark Nielsen 7-5 1-6 6-4 in the Japan F6 semi-final on carpet. The upset overturned the form book — Mark Nielsen came in leading the head-to-head 3–1. Atsuo Ogawa narrowed the head-to-head to 3–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2005-08-29 | Japan F9 | R16 | hard | Mark Nielsen | 6-4 6-4 |
| 2005-06-20 | Japan F7 | R32 | clay | Mark Nielsen | 6-1 6-1 |
| 2005-04-11 | Japan F1 | R32 | carpet | Atsuo Ogawa | 7-5 2-6 6-4 |
| 1999-10-25 | Japan F6 | R32 | carpet | Mark Nielsen | 6-2 6-0 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.