Samantha Stosur won her second singles match to give Australia a spot in the Fed Cup World Group by taking an unassailable 3-0 lead in their playoff with Germany on Sunday.
The fifth-ranked Stosur defeated Germany's No. 1 Andrea Petkovic 6-4, 6-1 in 1 hour, 14 minutes.
Petkovic, who is ranked 11th, was playing her first competitive match since returning from a lower back injury and was unable to prevent the US Open champion from dominating the second set.
Stosur also beat Germany's Angelique Kerber in straight sets on Saturday, before 50th-ranked Jarmila Gajdosova beat Julia Goerges - a player ranked 34 places above her - to leave the hosts facing relegation to World Group II.
Germany was forced into the playoff after losing to the Czech Republic in the first round in February.
After more than three months out, Petkovic was only set to play in Sunday's doubles match, but Germany coach Barbara Rittner brought in the 24-year-old against Australia's No. 1 in the ho...