Rebeka Masarova upset third-round favourite Maria Sakkari 6–4, 6–4 at the US Open on hard court in the first round on 28 August 2023. Sakkari entered as the heavy pre-match favourite at 1.27 odds, with Masarova priced at 4.17, yet the Swiss player delivered a composed performance to secure a straight-sets victory. Masarova's clinical execution in both sets proved decisive, as she broke through Sakkari's resistance with consistent play to claim the upset. The result marks a significant scalp for Masarova early in the tournament and represents a disappointing first-round exit for the seeded Greek player.