Deterioration of Dart's chances for US Open triumph amidst scorching temperatures and Kostyuk's aggressive playoff pressure

Harriet Dart's aspirations for progress at the US Open were dashed under oppressive New York heat as she was defeated 7-6 (10), 6-1 by Marta Kostyuk of Ukraine in the second round.

Having only reached the third round once before, this time on home soil at Wimbledon, Dart competed against Kostyuk for her best outcome yet in New York City. The seasoned player has been making notable strides recently, rising to a career-high ranking of 75 and maintaining strong competition with top contenders within the ATP/WTA rankings. She commenced at Flushing Meadow triumphantly against Chloé Paquet from France in her first matchup there since then.

The heat felt suffocating right off the bat, far more intense than usual both on and away from court surfaces; Kostyuk was among those feeling its impact most acutely as she sought relief by using ice packs for each thigh and one additional cooling pad placed atop her head during a brief respite.

Throughout much of the initial set, Dart displayed superior gameplay against an inconsistent Kostyuk who was struggling to find rhythm under extreme conditions; asserting herself more solidly in play exchanges made it seem probable she would secure victory early on until her first break point gave way at 5-3 and then again just before the deciding tiebreakers when serving for a set, including five consecutive points towards that end.

While Dart showcases commendable defensive skills along with excellent ability to redirect pace from both sides of baseline engagements - traits common among elite players at this level—her serve remains her weakest point under such high-stakes competition conditions; crucial moments in the opening set revealed faltering first serves and erroneous second serving attempts that proved fatal for Dart.

Following a brief respite from adversity, Kostyuk capitalized on these opportunities as she retired while two sets down due to shoulder issues—a significant achievement given her relatively lower ranking compared with many of the challengers remaining in this round; Frances Tiafoe similarly acknowledged preparation for extreme heat by carrying an excessive amount (20 shirts and three pairs) onto court during his own match, highlighting just how much players must acclimate themselves to such conditions.

Throughout these trials—be it battling intense physical discomfort or competing against formidable opponents like Kostyuk —both Dart & Tiafoe have displayed their resilience and determination; even in the face of considerable adversity, they've managed to maintain impressive performances thus far within these highly demanding tournaments.