Ostrava, Czech Republic, 10 February 2013 | AAP

Sam Stosur has lost in straight sets to Czech world No.18 Lucie Safarova in her opening Fed Cup match.

The 7-6(6) 7-6(4) result means the reigning champion Czechs lead 2-0 going into the final day of the best-of-five match tie.

World No.9 Stosur stretched to a 4-1 lead in the first set.

But at a 5-3 set point, a double fault from the Australian signalled a change of fortune from which Safarova carved a 6-5 lead, before taking the set in a tie break.

Mid-way through the second set Stosur called a medical time-out and was seen receiving sideline treatment to her lower leg.

The nature of the treatment is yet to be confirmed by the Australian camp.

Earlier on Saturday Jarmila Gajdosova lost 7-6(2) 6-3 to Czech world No.8 Petra Kvitova.

In Sunday’s reverse singles, Stosur takes on Kvitova and, if necessary, Gajdosova plays Safarova.

The final match scheduled for the tie is doubles featuring Australia’s Fed Cup debutante Ash Barty who joins Casey Dellacqua against Czech world No.3 pair Lucie Hradecka and Andrea Hlavackova.