Polona Hercog upset favourite Kiki Bertens 6–1 3–6 6–4 in the first round of Roland Garros on clay on 31 May 2021. Bertens, the pre-match favourite at 1.88 odds, started strongly to take the opening set 6–1, but Hercog regrouped to level at one set apiece with a 6–3 second-set victory. The decisive third set proved tight, with Hercog ultimately prevailing 6–4 to secure an upset win against the seeded Dutch player. The result represents a notable scalp for Hercog early in the tournament, suggesting improved form on the clay-court season.