Late additions to the lineup Tomas Berdych and Radek Stepanek won the doubles match to give the Czech Republic a 2-1 lead in the Davis Cup semifinal against Argentina.
They defeated Eduardo Schwank and Carlos Berlocq 6-3, 6-4, 6-3.
Czech captain Jaroslav Navratil replaced his announced doubles pair of Lukas Rosol and Ivo Minar with Berdych and Stepanek, using his top two players in a move to get an edge going into Sunday's decisive reverse singles.
Berdych may face an injured Juan Martin del Potro in the first reverse singles on Sunday. Stepanek may play Juan Monaco in the last match.
Del Porto has a sore left wrist, his non-racket hand, and his status for Sunday is unclear.
''There is nothing decided yet,'' Argentina assistant captain Mariano Zabeleta said.
Argentina is trying to reach its fifth Davis final. It has lost a record four finals, including last year against Spain. The Czechs won as Czechoslovakia in 1980.