British number one Johanna Konta was knocked out in the Pan Pacific Open last-16 in a straight-set defeat by Croatia’s Donna Vekic.
World number 43 Konta lost 6-3 7-5 in one hour 22 minutes in Tokyo.
Having lost the opening set, Konta, 27, was 4-1 up and had a chance to serve for the second before the 22-year-old fought back.
Vekic, who beat Sloane Stephens in the opening round, faces French second seed Caroline Garcia in the quarter-finals.
Garcia, the world number four, beat Russia’s Anastasia Pavlyuchenkova 6-4 2-6 7-5 to reach the last eight.
Vekic earned an early break and held on to edge a tight first set from Konta, but the Briton looked to be in control of the second.
Konta was two breaks up at one point and holding a 4-1 lead, and then had the chance to serve for the set before Vekic recovered to take a 6-5 advantage.
The Briton, who racked up 38 unforced errors in the match, then lost a second successive service game to love as world number 45 Vekic progressed.
“I played really well towards the end of the match and I am really happy to win this in two sets,” said Vekic.