Guillermo Duran defeated Guillermo Bujniewicz 6-4 6-4 in the Argentina F21 round of 16 on clay. The upset overturned the form book — Guillermo Bujniewicz came in leading the head-to-head 2–1. Guillermo Duran narrowed the head-to-head to 2–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2010-04-26 | Argentina F4 | SF | clay | Guillermo Duran | 6-1 6-0 |
| 2009-04-27 | Argentina F3 | R32 | clay | Guillermo Bujniewicz | 6-2 6-3 |
| 2007-09-24 | Bolivia F3 | R16 | clay | Guillermo Bujniewicz | 6-2 6-1 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.