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Sabalenka emerged on court at Arthur Ashe Stadium at seven minutes past midnight after Novak Djokovic's shock exit from the tournament to Australia's Alexei Popyrin, and consecutive upsets looked to be on the cards. 

However, the Belarusian responded from a disappointing opening set as she looks to avenge her defeat in the showpiece match against Coco Gauff a year ago.

The world No.2 set up a meeting with Belgium's Elise Mertens as she emerged a 2-6 6-1 6-2 victor in one hour and 40 minutes in New York.

"I don't know what I did, I was just trying to stay low, put as many balls as I can back on that side," Sabalenka said.

"She played incredible tennis in the first set. It was really tough to change it."

"I'm really happy I was able to turn around this match and get this really difficult win. Thanks so much for staying that late."

Sabalenka's encounter with Alexandrova was the latest starting match at the US Open, beating Gabriela Sabatini and Beverley Bowes's meeting in 1987 that started at midnight.

The Belarusian, however, will be hoping for a much improved performance in the next round, having produced 27 unforced errors throughout the contest and serving four double faults.