Maria Sharapova: Defeated Agnieszka Radwanska in straight sets
Maria Sharapova sent Russia into the semi-finals of the Fed Cup as she defeated Poland's Agnieszka Radwanska 6-1 7-5 to give her country an unassailable 3-0 lead.
The doubles pairing of Anastasia Pavlyuchenkova and Vitaliya Diatchenko later made it 4-0 as they beat Klaudia Jans-Ignacik and Alicja Rosolska 6-4 6-4.
Following Sharapova's victory over Urszula Radwanska in straight sets on Saturday, combined with a three-set win for veteran Svetlana Kuznetsova over Urszula's sister Agnieszka, Russia cruised into the last four.
French Open champion Sharapova is playing just her fourth Fed Cup tie since her 2008 debut but to make the Olympics next year all players have to make themselves available for the annual women's team tournament.
"It is a very important win for me," said Sharapova. "Playing for the national team there is always added pressure."
In front of a partisan home crowd of some 15,000, Sharapova, who recently lost the Australian Open final to Serena Williams, improved her record against the world No 8 to 12 wins against just two defeats.
Radwanska saved two match points at 2-5 down in the second set to draw level at 5-5, but ran out of steam as five-time Grand Slam winner Sharapova closed out the match in less than two hours.
Russia now progress to a semi-final date with Germany after Andrea Petkovic sealed a 3-1 victory over Australia.
Petkovic endured another gruelling three-set marathon to complete a 6-3 3-6 8-6 win over Jarmila Gajdosova with the third set taking nearly an hour.
It was the second time in 24 hours Petkovic was carried to victory by the vocal 4,000-strong crowd in Stuttgart, having beaten Samantha Stosur 12-10 in the third set on Saturday after three hours 13 minutes of tennis.
Having been 4-2 down in the crucial third, Petkovic showed her composure by converting her second match point to secure Germany's win and keep them bidding for a second straight final appearance.
Happy holders
Holders the Czech Republic set up a semi-final against France on Sunday after Karolina Pliskova beat Gabriela Dabrowski 6-4 6-2, giving the visitors an insurmountable 3-0 lead over Canada.
Pliskova needed only 72 minutes to capture the clincher, to follow up her win on Friday when, on her Fed Cup debut, overcame teenager Francoise Abanda. The Czechs improved to 6-0 in all-time Fed Cup ties against Canada, but this was their first meeting since 2002.
France are also through to the semi-finals for the first time since 2007 after coming from behind to record a 3-2 victory over Italy.
Caroline Garcia and Kristina Mladenovic followed up their earlier singles victories by beating the world's top-ranked doubles pair Sara Errani and Roberta Vinci 6-1 6-2 to complete the comeback.
Venus Williams defeated Maria Irigoyen of Argentina 6-1 6-4 to advance the United States to the Fed Cup play-offs in April and a chance to return to the World Group.
Williams' victory on outdoor clay gave the United States an unassailable 3-1 lead in the best-of-five World Group II tie.
Earlier on Sunday, Paula Ormaechea of Argentina defeated Coco Vandeweghe 6-4 6-4 after Vandeweghe filled in for Serena Williams, who did not play because of illness.
Venus and Serena gave the United States a 2-0 lead on Saturday, defeating Ormaechea and Irigoyen.