Joanna Sakowicz Kostecka defeated Karolina Kosinska 6-1 6-4 in the Gdynia 10K round of 32 on clay. The upset overturned the form book — Karolina Kosinska came in leading the head-to-head 2–0, but Joanna Sakowicz Kostecka had been the form player, winning 3 of their last 7 on clay. Joanna Sakowicz Kostecka claimed a first win over Karolina Kosinska in three meetings, narrowing the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 2005-08-15 | Kedzierzyn Kozle 25K | R16 | clay | Karolina Kosinska | 6-4 6-2 |
| 2004-07-05 | Torun 25K | R32 | clay | Karolina Kosinska | 6-4 3-6 6-4 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.