World number one, Naomi Wozniacki has made a shocking exit from the Miami Open after being stunned by Hsieh Su-wei on Saturday.
The two-time grand slam champion fell to a surprise loss to Hsieh on a day that her rivals, Caroline Wozniacki and Petra Kvitova moved into the last 16 of the Miami Open.
Osaka had won her previous two meetings with Hsieh ranked 27th in the world, but the 33-year-old claimed a surprise 4-6 7-6 (7-4) 6-3 win.
Hsieh Su-wei records a rare victory over world number one, Naomi Osaka
The 21-year-old Osaka was up a set and a break, only to give up her advantage before losing four straight points in the second-set tie-break.
Osaka took a 2-0 lead in the decider, but lost four straight games from 3-2 up to make an early exit.
Kvitova was tested before getting past Donna Vekic, while 2017 runner-up Wozniacki was also challenged in the third round.
It was a good day for the seeds at the WTA Premier event, but not so for Japanese star Osaka.
Kvitova survived a huge test against Vekic, progressing thanks to a 6-4 3-6 6-4 victory.
The Czech third seed lost to Croatian Vekic when they met in St Petersburg earlier this year, but a single break in the final set proved decisive.
Wozniacki is well-placed for another deep run after overcoming qualifier Monica Niculescu 6-4 7-6 (7-4).
With Osaka's shock loss, the top half of the draw has opened up for Wozniacki.