Yaoki Ishii defeated Tetsuya Chaen 3-6 6-1 7-6 in the Japan F4 round of 16 on hard. The result followed the form book — Yaoki Ishii came in leading the head-to-head 3–2. Yaoki Ishii extended the head-to-head to 4–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2008-06-30 | Japan F7 | R16 | hard | Yaoki Ishii | 6-4 6-1 |
| 2007-05-07 | China F1 | QF | hard | Yaoki Ishii | 6-0 6-2 |
| 2006-04-17 | Japan F2 | SF | carpet | Tetsuya Chaen | 6-2 3-6 6-4 |
| 1998-03-25 | Japan F2 | SF | carpet | Tetsuya Chaen | 6-4 6-3 |
| 1997-11-17 | Japan 2 Masters 1 | QF | hard | Yaoki Ishii | 7-5 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.