Petra Kvitova's quest to claim the world number one ranking was ended following a surprise Miami Open loss to Ashleigh Barty, while Anett Kontaveit reached the semi-finals.
Australian Open runner-up and Czech third seed Kvitova lost 7-6 (8-6) 3-6 6-2 to Barty in an entertaining late-night clash in Miami on Tuesday.
Kvitova needed to reach the final of the Premier Mandatory tournament to have a chance of replacing Naomi Osaka as the WTA's top-ranked player.
However, Kvitova was upstaged by Australian 12th seed Barty, who claimed her first career win over the Czech star as she confirmed her rise into the top 10.
Barty – blitzed by Kvitova in the quarter-finals of the Australian Open in January – overcame a two-hour rain delay to set up a semi-final showdown with Kontaveit at the Miami Open.
Kontaveit emerged from the jaws of defeat to advance to her first Premier Mandatory semi-final at the expense of Hsieh Su-wei.
Down 4-0 and 5-3 in the final set, 21st seed Kontaveit rallied to win 3-6 6-2 7-5 in Tuesday's earlier match.
Hsieh won 16 of the first 19 points of the deciding set – including 12 in succession – as she raced out to a commanding four-game lead, but Kontaveit surged back to claim a final-four berth.