American Christina McHale pummelled Belgium's Elise Mertens 6-4, 6-1 to reach the Japan Women's Open semi-finals Friday as the last two remaining seeds in Tokyo fell by the wayside.

Defending champion McHale faced surprisingly little resistance from the third seed before Zarina Diyas came from a set down to beat fellow Kazakh Yulia Putintseva 4-6, 6-1, 6-3 in the day's second quarter-final.

Eighth seed Putintseva's exit left organisers hoping Japanese qualifier Miyu Kato could continue her dream run after a week of upsets and the early loss of local favourite Kimiko Date in her final tournament at the age of 46.

And Kato did not disappoint, again punching above her weight as she thumped Date's conqueror Aleksandra Krunic of Serbia 6-1, 6-3.

"Once I won the first set I relaxed a little more," said McHale, who faces Diyas in the last four. "I served better in the second set and pulled it out."

In Friday's late match, Croatian Jana Fett beat China's Wang Qiang 6-3, 4-6, 6-3 to set up a semi-final with Kato.

Source: AFP