Guillermo Alcorta Olarra defeated Guillermo Olaso 7-5 6-1 in the Spain F42 round of 16 on hard. The upset overturned the form book — Guillermo Olaso came in leading the head-to-head 2–0. Guillermo Alcorta Olarra claimed a first win over Guillermo Olaso in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2009-07-13 | France F12 | QF | clay | Guillermo Olaso | 7-6(4) 6-1 |
| 2007-11-05 | Spain F40 | R16 | hard | Guillermo Olaso | 3-6 6-1 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.