World No.39 Jarmila Gajdosova and the 64th-ranked Jelena Dokic are vying for the second singles berth, while French Open mixed doubles champion Casey Dellacqua rounds out Australia's team for the World Group II tie against Switzerland on February 4-5.
Victory over the Swiss would thrust Australia into a playoff in April for the right to return to the elite eight-nation World Group in 2013.
"Switzerland is a team our Fed Cup girls know very well," Australian captain David Taylor said on Saturday.
"It will be the fourth time we have played since 2001 and we have been fortunate to win three of the most recent ties against the Swiss and I know the girls are very motivated to keep that streak alive.
"Going from an Australian summer, where the girls have played on hardcourts, to a slow indoor claycourt, in the Swiss Alps, is quite a contrast but I am confident they will make the adjustment."
Stosur and Gadjosova both crashed out in the first round of the Australian Open this week, but Taylor had no doubts his singles aces would quickly rebound.
"Sam and Jarka have had very challenging summers but I know they are extremely motivated to get back on track in Switzerland," he said.
Dokic is returning to the Fed Cup fold for the first time since 2009, while Dellacqua hasn't featured since 2010.
"Casey has played a significant amount of matches on the Australian Pro Tennis Tour and has stepped up with a few wins at WTA tour level recently," said Australian coach Nicole Bradtke.
"Jelena also has been able to post some wins recently in Sydney and Melbourne and I'm sure 2012 will see them both climbing back toward the top 50.
"They both deserve the opportunity to represent their country again."
The tie is being hosted in Fribourg and marks the fifth time the two countries have met.
Australia leads 4-1 in the head-to-heads.
Australia were dumped from the World Group last year with a shock 3-2 playoff loss to Ukraine in Melbourne, but haven't lost an away tie since 2008.