Slovakia's Dominika Cibulkova battled back from a set down to beat Anastasia Pavlyuchenkova and put her side into the lead in their Fed Cup semi-final clash with hosts Russia on Saturday.
Cibulkova, who is 15th in the WTA rankings, won 5-7, 6-1, 6-4 in a match that lasted two hours 31 minutes.
"It was a very hard win," Cibulkova said. "I started nervously and made too many mistakes in the first set.
"In the second I forced myself to battle for every single ball and it paid off as I managed to come back into the match, although I had luck on my side on several occasions.
Pavlyuchenkova broke three times to win an opening set that lasted one hour four minutes, but Cibulkova hit back to claim a commanding 4-0 lead in the second.
Pavlyuchenkova broke back, but the 23-year-old Slovak went on to square the match at one set all and then made a decisive break in the seventh game of the deciding set.
Maria Kirilenko and Daniela Hantuchova meet in the second singles rubber later before the reverse singles and the doubles take place on Sunday.
The winner will face either Italy or Czech Republic in the final.