Sebastian Decoud defeated Matias Oneille 6-4 6-4 in the Argentina F5 round of 32 on clay. The upset overturned the form book — Matias Oneille came in leading the head-to-head 3–0. Sebastian Decoud claimed a first win over Matias Oneille in four meetings, narrowing the head-to-head to 3–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2003-08-25 | Argentina F2 | R32 | clay | Matias Oneille | 6-1 6-1 |
| 2000-05-22 | Argentina F6 | R16 | clay | Matias Oneille | 4-6 7-5 6-0 |
| 2000-05-01 | Chile F6 | R16 | clay | Matias Oneille | 6-3 6-3 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.