Bad Gastein, 5640 Bad Gastein, Austria, 23 July 2015 | AP/AAP

Sam Stosur has stormed into the WTA Gastein Ladies quarterfinals by beating Klara Koukalova of the Czech Republic 6-1 6-0.

Stosur, the second-seeded Australian, saved three break points in the opening set and then dominated the second.

Despite double-faulting on match point twice, she nonetheless closed out the win in just 49 minutes.

“I guess the score looked pretty easy, but you never can let up in matches even if you feel like you’re going really comfortably,” Stosur said.

“I’ve been in enough matches where it’s turned around to know that you have to stay concentrated and keep doing all the right things to make sure you finish it off.”

In her first quarterfinal since winning her seventh career title in Strasbourg in May, Stosur will play Danka Kovinic of Montenegro, who defeated lucky loser Richel Hogenkamp of the Netherlands 6-3, 6-1.

Stosur ousted Kovinic in straight sets in the opening round of Wimbledon just a few weeks ago.

Polona Hercog of Slovenia also reached the quarters by ousting fifth-seeded Lucie Hradecka of the Czech Republic 6-3 6-2.

Meanwhile, top-seeded Sara Errani and No. 7 Anna Karolina Schmiedlova won their first-round matches.

Errani sweated to get past Aliaksandra Sasnovich of Belarus 6-4 6-4. The 19th-ranked Italian dropped serve three times and held off eight more break points.

Schmiedlova, who beat Errani in the final at Bucharest last Sunday, overcame a slow start to defeat Patricia Mayr-Achleitner of Austria 3-6 6-2 6-0. The Slovakian was broken twice in the opening set but won nine straight games from 3-2 in the second set.

Suffering from persistent back problems, 2011 finalist Mayr-Achleitner said after the match she will retire from competitive tennis at the end of the season.

In the only other remaining first-round match, Johanna Larsson of Sweden downed Stefanie Voegele of Switzerland 6-2 6-2.