The surprise announcement came after seven-time Grand Slam winner Venus shook off a scratchy start in which she squandered an early 3-0 lead to allow Dutch opponent Richel Hogenkamp to draw level at 3-3, before fighting back to prevail 7-5 in the first set.
A demoralized Hogenkamp, who had used a combination of accurate serves and deft slices to hold her own in the first set, went down tamely in the second, 6-1.
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.
Team captain Kathy Rinaldi then announced the Williams sisters would play together in the doubles tie against Lesley Kerkhove and Demi Schuurs, in what will likely be a victory lap before the home crowd in Asheville, North Carolina.
Serena will be playing her first competitive match since winning her 23rd Grand Slam title at the 2017 Australian Open.
The 36-year-old American took time away from the sport to give birth to her daughter and get married.
Czechs in semis
Petra Kvitova led the Czech Republic into a 10th successive Fed Cup semi-final yesterday.
Two-time Wimbledon champion Kvitova, playing in her first Fed Cup tie since she was attacked by a knife-wielding burglar at her home in December 2016, eased past Belinda Bencic 6-2, 6-4 to give the Czechs an unassailable 3-0 lead over Switzerland in Prague.
Kvitova, 27, had already won her opening singles on Saturday, beating Viktorija Golubic 6-2, 1-6, 6-3.
“I’m very happy, I was very calm, relaxed throughout the match. I played a great match, I didn’t lose my serve once,” said Kvitova who announced her return to form with the St Petersburg WTA title last weekend.
“I didn’t expect to stand in for Karolina (Pliskova, down with flu), but it was way above my expectations.”
The Czechs, who have won the Fed Cup 10 times, will face either 2017 runners-up Belarus at home in April’s semi-finals, or travel to Germany.
In Minsk, the Belarus against Germany tie was being decided in the doubles after Tatjana Maria downed Vera Lapko 6-4, 5-7, 6-0 and home player Aryna Sabalenka defeated Antonia Lottner 6-3, 5-7, 6-2 to make the score 2-2.
In La Roche sur Yon, the tie between France and Belgium was also going down to the wire after French number one Kristina Mladenovic beat Australian Open semi-finalist Elise Mertens 6-4, 6-4 before Alison Van Uytvanck eased past Pauline Parmentier 6-1, 6-3 to pull the hosts level.