Tomáš Macháč defeated Joao Fonseca 7–6, 6–2, 6–3 in the first round of the US Open on hard court on 27 August 2025, confirming his status as the pre-match favourite. Macháč's victory was methodical rather than dominant; the opening set went to a tiebreak before he asserted control in the second and third frames. Fonseca, competing at a Grand Slam stage, struggled to maintain the intensity required against the Czech player's composed performance. The result extends Macháč's early-round record at Flushing Meadows and positions him favourably for the second round.