Hiromasa Oku defeated Masaki Sasai 6-1 6-1 in the Guam F1 round of 32 on hard. The upset overturned the form book — Masaki Sasai came in leading the head-to-head 2–0, but Hiromasa Oku had been the form player, winning 1 of their last 4 on hard. Hiromasa Oku claimed a first win over Masaki Sasai in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2015-03-23 | Japan F3 | Q16 | hard | Masaki Sasai | 6-0 1-0 |
| 2011-06-20 | Japan F7 | R32 | grass | Masaki Sasai | 6-3 6-1 |
Averages over each player's completed matches in the selected window (19 vs 12). ATP, WTA & Challenger.
Each player's serve crossed against the other's return, converted to expected hold of serve. Recent completed matches, ATP, WTA & Challenger. About