Safarova, at No. 28, is the highest ranked Czech women's player but her illness led Czech captain Peta Pala to turn to Zahlavova Strycova and hold Safarova back for a possible doubles appearance.
The Czechs, who won Fed Cup titles in 2011 and '12, head to Spain for a best-of-five quarterfinal series. The winner takes on either defending champion Italy or the United States in the semifinals in April.
Zahlavova Strycova will go against Spain's Carla Suarez Navarro in the first match Saturday and Klara Zakopalova faces Maria-Teresa Torro-Flor in the second. Suarez-Navarro opens Sunday's play versus Zakopalova and Zahlavova Strycova and Torro-Flor are matched against each other for the fourth singles match of the series.
Pala has put Safarova on his expected doubles team, playing with Andrea Hlavackova against Spain's Lara Arruabarrena and Silvia Soler-Espinosa in the final match of the series.
Zahlavova Strycova is 6-4 in Fed Cup singles matches while Suarez Navarro is 7-7 but the Spanish player takes a 3-1 career mark against Zahlavova Strycova into Saturday's match. All of those matches were on clay, the same surface as this weekend's series will be played on.
Zakopalova is 7-4 in Fed Cup singles. Torro-Flor is relatively inexperienced with a 1-0 Fed Cup mark but she beat Zakopalova last year in their only WTA meeting.