After that, Dusan Lajovic of Serbia will take on Tomas Berdych.
Lajovic has replaced Janko Tipsarevic, the world number 36, who has been ruled out with a heel injury.
In Saturday's doubles, Serbia's Ilija Bozoljac and Nenad Zimonjic are due to face the Czech Republic's Jan Hajek and Lukas Rosol.
But the Czechs are almost certain to bet on Berdych and Stepanek for the doubles too as the two have lost only one of their 14 Davis Cup doubles rubbers together since teaming up in 2007.
In Sunday's reverse singles, Djokovic will face Berdych and Lajovic will then take on Stepanek.
Serbia won their only Davis Cup title in 2010, beating France 3-2 in Belgrade.
The Czechs, playing their third final in five years, lifted the trophy last year after downing Spain 3-2 in Prague.