Defending champion Elina Svitolina joined Simona Halep in the Dubai Tennis Championships quarter-finals with victory on Wednesday.
While Elina Svitolina, Simona Halep, Petra Kvitova and Angelique Kerber all won on Tuesday, Naomi Osaka suffered an upset.
Simona Halep won five games in a row in the deciding set of a thrilling contest with Elina Svitolina to reach her first final of the season.
Simona Halep will take on Elina Svitolina in the last four in Doha, while Angelique Kerber will be the favourite to get past Elise Mertens.
Simona Halep battled back in a second-set tie-break to see off Julia Goerges and set up a semi-final with Elina Svitolina in Doha.
Simona Halep and Angelique Kerber sealed their places in the last eight in Doha with straight-sets victories on Wednesday.
US Open champion Naomi Osaka eased past Elina Svitolina in the Australian Open quarter-finals.
With the world number one knocked out in Melbourne, four players are in contention to take over at the summit of the WTA rankings.
There were no major upsets in the women's singles on day four of the Australian Open, with Serena Williams and Naomi Osaka winning.
Elina Svitolina says the way she came through a tense final set showed she has the mental strength to succeed at the highest level.