Serena Williams made her long-awaited comeback to tennis on Sunday but the 23-time Grand Slam title winner and former world number one suffered defeat, playing alongside big sister Venus in a Fed Cup dead rubber.
They lost 6-2, 6-3 to the Dutch pairing of Lesley Kerkhove and Demi Schuurs, with 36-year-old Serena appearing particularly slow on her feet and rusty after more than a year away from the sport.
The result took some of the shine off the United States' otherwise decisive victory, leaving the final score 3-1 for the defending champions, booking a semi-final clash against France in April.
It was Serena's first competitive match since winning her 23rd major at the 2017 Australian Open, and the first time the sisters had played doubles together in this tournament since 2003.
The American star took time away from the sport to give birth to her daughter Alexis Olympia and get married, to Reddit co-founder Alexis Ohanian.
Both were in attendance over the weekend, seated just behind the players' box.
Serena told reporters on Friday that her path back had been full of "ups and downs" but credited her sister with helping her find her rhythm.
There had been speculation she may drop out of Sunday's doubles match, but team captain Kathy Rinaldi confirmed her participation after Venus won her singles match against Richel Hogenkamp earlier to seal victory for the United States, 3-0.
"Serena's gonna be joining her sister Venus!" she announced, to roars of approval before Williams appeared dressed in a white top, dark blue shorts topped off with a red headband.
The sisters have won 22 doubles titles together, the last of which was Wimbledon in 2016.
They enjoyed enormous support over the weekend from the sold-out 5,200-capacity crowd in the mountainous city of Asheville, North Carolina, famous for its historic architecture, breweries and vibrant art scene.
"To play the two Williams sisters, it's amazing because we won the match," said Kerkhove.
"We knew it just 30 minutes before the match. We just both gave it our all and we just had nothing to lose."
Venus' participation meant there was no room for Lauren Davis, the US' fourth player.
The seven-time Grand Slam winner, who enjoyed a renaissance year in 2017, earlier shook off a scratchy start to prevail 7-5, 6-1 in her singles match, ensuring the US booked their place in the semi-finals against France.
Venus credited teammate CoCo Vandeweghe, who scored a hard-fought win over Hogenkamp the day before, for paving the way.
"Honestly I like to think CoCo wore her down some. That gave me an opportunity to be able to close it out for the USA," she said.
"There was a lot of pressure for me to close it out, for her to be able to stay in, and I was able to handle it a little better," she added.