Dominik Koepfer defeated Reilly Opelka 6–4, 6–4, 7–6 at the 2019 US Open in the first round on hard court, delivering an upset against the pre-match favourite. Opelka, seeded higher in the betting odds at 1.42 to Koepfer's 3.13, could not maintain the form required to progress, succumbing to the German's consistent play across three sets. Koepfer's straight-sets victory demonstrated his ability to compete against a bigger-serving opponent on the hard courts of Flushing Meadows, where such surfaces typically favour tall, aggressive players. The result marked a significant scalp for Koepfer early in the tournament and set up a favourable path through the draw for the German.