Petra Kvitova lost 7-6 (8-6) 3-6 6-2 to Ashleigh Barty in an entertaining quarter-final clash in Miami on Tuesday.
Hsieh Su-wei completed a third-round upset at the Miami Open as world number one Naomi Osaka was knocked out.
Elina Svitolina's reign as Dubai Tennis Championships queen is over as she lost to Belinda Bencic, who faces Petra Kvitova in the final.
Both Belinda Bencic and Hsieh Su-wei produced excellent comebacks on Thursday, when Simona Halep was dumped out in Dubai.
Defending champion Elina Svitolina joined Simona Halep in the Dubai Tennis Championships quarter-finals with victory on Wednesday.
Simona Halep and Angelique Kerber sealed their places in the last eight in Doha with straight-sets victories on Wednesday.
Japanese star Naomi Osaka was down a set and 4-1 in the second before rallying to a 5-7 6-4 6-1 win in Melbourne on Saturday.
Caroline Wozniacki made a positive start to the season in Auckland, while Maria Sharapova is through to the last eight in Shenzhen.
Jelena Ostapenko was thrashed by Monica Niculescu in Shenzhen, while Venus Williams made a winning start to 2019.
Timea Bacsinszky was swept aside by Karolina Pliskova, who will now face second seed Caroline Garcia in the Tianjin Open final.