Saturday's earlier fixture had seen America's top-ranked Coco Vandeweghe beat Aliaksandra Sasnovich 6-4 6-4.

However, 19-year-old Sabalenka, playing as Belarus number one for the first time this year in the absence of Victoria Azarenka, produced a battling display to defeat Stephens 6-3 3-6 6-4 in just over two hours to delight the partisan crowd at the Chizhovka Arena.

Stephens, the world number 13, has not won a match since her shock triumph in New York in September, and was soon 3-0 down as the first set slipped away.

Although the American rallied to level in the second set, both players serve faltered in the decider, with Sabalenka eventually claiming match point at the fourth attempt.

Earlier, Vandeweghe had coasted through the opening set before seeing off a brief recovery from Sasnovich, who had been unbeaten in her 2017 Fed Cup matches.

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