Guillermo Bujniewicz defeated Guillermo Duran 6-2 6-1 in the Bolivia F3 round of 16 on clay. The upset overturned the form book — Guillermo Duran came in leading the head-to-head 2–1, but Guillermo Bujniewicz had been the form player, winning 5 of their last 10 on clay. Guillermo Bujniewicz narrowed the head-to-head to 2–2.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2011-10-24 | Argentina F21 | R16 | clay | Guillermo Duran | 6-4 6-4 |
| 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 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.