Madrid, Spain, 10 May 2019 | AAP

Ash Barty’s first Premier-level clay-court quarterfinal ended in defeat as former world No.1 Simona Halep halted the Australian’s 11-match winning streak with victory at the Madrid Open.

The Romanian kept her hopes of regaining the world No.1 ranking alive with a 7-5 7-5 win, although an occasionally off-balance Barty battled gamely before losing to a top-five player for the first time this year.

In doubles, Sam Stosur and Shuai Zhang, the reigning Australian Open champions, went down to fifth seeds Hsieh Su-Wei and Barbora Strycova 6-2 6-4 in the quarterfinals.

Barty twice broke back to level sets on Thursday when Halep seemed on track for an easier progression to the semifinals.

However, the world No.3 was never seriously threatened as Barty, who beat Halep on Sydney’s hard courts in January, committed 37 unforced errors.

The world’s premier clay-court player also relied on an accurate first serve (87 per cent) to condemn Barty to her first defeat since Indian Wells and dash hopes of back-to-back semifinal appearances after her Miami Open triumph last month.

Halep now faces unseeded Swiss Belinda Bencic, who recovered from 3-5 down in the third set to beat world No.1 Naomi Osaka for the first time.

With Osaka out, Halep, the reigning French Open champion, can retake top spot by winning her third Madrid title.

Earlier, Barty’s 4-6 6-1 6-2 third-round defeat of Yulia Putintseva improved the 23-year-old Queenslander’s win-loss record in 2019 to 23-3, matching Lleyton Hewitt’s remarkable start to 2003.

Barty realised the enormity of her task against Halep, the owner of six titles on European clay, when the 27-year-old described her 6-0 6-0 third-round demolition of world No.46 Viktoria Kuzmova as the finest performance of her career.