Italy have joined Australia and Germany in the semi-finals of the Fed Cup following a 3-1 success over the United States.
The Italians will not learn their opponents until Monday after Spain's clash with Czech Republic was delayed due to heavy rain in Seville.
Italy, who are seeking a fifth Fed Cup success in nine years were without stars Sara Errani and Flavia Pennetta while the USA were missing Serena Williams and Sloane Stephens.
Karin Knapp claimed the decisive third point for Italy, giving them an unbeatable 3-0 lead with a 6-3 7-5 victory over American Alison Riske.
Knapp broke Riske seven times, and while the Italian's nerves got the better of her in her first two chances to serve for the match, she finished it off in style with a love game punctuated by a service winner on her first match point.
"I got a little bit nervous," Knapp admitted. "I got a little bit of emotion. At the end, the last game, I served again better. I think this was the key."
In the meaningless doubles match, Keys and Lauren Davis teamed up to beat Nastassja Burnett and Alice Matteucci 6-2 6-3 to prevent the whitewash.
Ensured their place
Australia ensured their place in the last four for the first time in 21 years with a crushing Samantha Stosur-inspired 4-0 defeat of Russia in Hobart.
The 2011 US Open champion added to her Saturday singles win when seeing off Fed Cup newcomer Victoria Kan 6-2 6-3 in Sunday's opening rubber to secure an unassailable 3-0 lead.
Ashleigh Barty and Casey Dellacqua sealed a 4-0 clean sweep over the Russians with an emphatic 6-1 6-3 doubles win over Irina Khromacheva and Valeria Solovyeva.
First though they will have to overcome Germany, who qualified 3-1 after Angelique Kerber defeated Slovakia's Australian Open runner-up Dominika Cibulkova 6-3 7-6 (7/5) in the first of the reverse singles in Bratislava.
Kerber had already beaten Daniela Hantuchova 7-6 (11/9) 6-1 in the second of Saturday's two singles, after Andrea Petkovic had saved a match point en route to a 1-6 7-6 (9/7) 6-2 win over Cibulkova.
Slovakia picked up their point courtesy of Jana Cepelova and Magdalena Rybarikova's 4-6 6-3 10-7 doubles win over Julia Goerges and Anna-Lena Groenefeld.