2019 US Open champion Bianca Andreescu made a winning return to New York overnight, but it took a third set comeback to eventually see off Viktorija Golubic, 7-5, 4-6, 7-5 in a math that ran to the early hours.
The No.6 seed had to fight for the win against the 45th-ranked Swiss.
Andreescu played a solid first set but Golubic built a 5-3 lead before the Canadian responded.
It took a a 14-minute game that went to deuce seven times to break Golubic for the set.
The at 2-2 in the second Andreescu asked to see q doctor, complaining she was feeling unwell.
She returned broke serve but Golubic fought back to level the match.
Andreescu took a 2-1 lead in the third before Golubic broke through for a 3-2 lead.
Golubic’s baseline pressure pushed Andreescu hard, forcing several errors but the young Canadian hung in and despite facing an early exit at one stage, hit three winners to level at 4-4.
After holding to 6-5, Andreescu broke Golubic to seal her comeback as the clock struck 12.45am.
The Canadian will face American Lauren Davis in the second round.