Vinci earned her second straight-set win over Kvitova in less than a week. She beat the former Wimbledon champion in the final last weekend in Poland. That gave Vinci a career-high ranking of No. 12.
However, if the best-of-five series goes down to the doubles, Italy captain Corrado Barazzutti can switch to Errani and Vinci, the top-ranked team on the WTA Tour.
Slovakia stuns Russia, takes 2-0 lead
MOSCOW -- Slovakia stunned favored Russia by taking a 2-0 lead after the opening singles in the Fed Cup semifinals on Saturday.
Dominika Cibulkova rallied to beat Anastasia Pavlyuchenkova 5-7, 6-1, 6-4 in the opening singles. Daniela Hantuchova followed with a 6-2, 6-4 victory over Maria Kirilenko to put Slovakia one point away from advancing to the final for the first time since winning the title in 2002.
Hantuchova was chosen to play over the higher-ranked Magdalena Rybarikova. She broke Kirilenko twice in the first set and in the seventh game of the second on indoor clay at Krylatskoye Ice Stadium in Moscow.
Hantuchova improved to 35-16 in Fed Cup matches.
The winner will face two-time defending champion Czech Republic or Italy in the final on Nov. 2-3.
Spain grabs 2-0 lead
Suarez won the first set with relative ease on the outdoor clay court at Real Club de Polo tennis club.
Spain's top-ranked player took a 4-1 lead before losing three straight games. But Doi hit her ninth double-fault to drop serve, allowing Suarez to wrap up the match when the Japanese player netted her return.
Soler-Espinosa's reliable serve helped her ease past Morita. She was broken only once in the match.
Reverse singles and doubles will be played Sunday.
Information from The Associated Press was used in this report.