British pair Sonay Kartal and Katie Boulter were knocked out in the US Open first round as conditions heated up in New York.
Kartal, who has been managing a knee niggle in recent months, suffered physically in a 6-3 1-6 6-1 defeat against Brazilian 18th seed Beatriz Haddad Maia.
A bizarre deciding set saw a struggling Kartal trail 3-0 before being handed a lifeline when Haddad Maia’s movement also became hampered – seemingly down to cramp.
Points became slow and laboured in testing conditions – but neither player refused to give in.
Haddad Maia lost serve for 3-1 as she could barely walk but recovered sufficiently, helped by the vocal support of a boisterous set of Brazilian fans, to serve out a remarkable victory.
Kartal, who was making her debut in the US Open main draw, also appeared to be struggling with the knee problem which she had strapped during her memorable run to the Wimbledon fourth round in July.
Boulter, 29, lost 6-4 6-4 to Ukrainian 27th seed Marta Kostyuk as she was unable to turn around her Grand Slam struggles.
The powerful baseliner, who has never reached the second week of a major, has been out of form this season and seemed to lack confidence against Kostyuk.
Saving five match points as she served at 5-3 illustrated how Boulter will not stop fighting and helped her create three break points in the 10th game.
However, Kostyuk recovered to serve out the match and move into the second round.