World number one Ashleigh Barty remains unstoppable on the red clay, but next faces the only woman to beat her since February.
Ash Barty will face Petra Kvitova in Madrid after defeating Iga Swiatek to extend her impressive record against top-10 opponents.
Ash Barty will face Iga Swiatek at the Madrid Open after surviving a difficult test against Tamara Zidansek. Petra Kvitova also won through.
Elina Svitolina led Jil Teichmann 5-1 in the final set but the Swiss came storming back to go through at the Caja Magica.
As against Karolina Pliskova and Elina Svitolina, Ash Barty came from a set down to beat Aryna Sabalenka in the Stuttgart Open final.
The Stuttgart Open is the only major clay court tournament Simona Halep is yet to win, and her wait will go on for at least another year.
Ash Barty and Simona Halep are on course to meet in the Stuttgart Open final after both reached the tournament's semi-finals on Friday.
It was a comfortable debut at the Stuttgart Open for Ash Barty, though it was a trickier outing for Petra Kvitova.
World number one Ash Barty's eight-match winning run was ended by 71st-ranked Paula Badosa in Charleston.
World number one Ashleigh Barty won over Shelby Rogers but top 10 seeds Petra Kvitova and Garbine Muguruza both bowed out on Thursday.