Britain's Heather Watson lost to Canadian qualifier Aleksandra Wozniak in the Aegon Classic first round.
A day after reclaiming the British number one ranking, the 22-year-old spurned three match points in a 2-6 7-5 6-4 defeat in Birmingham.
The loss meant Watson missed out on a second-round encounter with her compatriot Johanna Konta.
Konta, Britain's third-ranked player, beat 14th seed Kurumi Nara 6-3 6-1 and will face Wozniak for a last-16 place.
Watson was a set and 4-1 up before losing a match lasting two hours and 13 minutes.
She said: "I got pushed back and wasn't playing as aggressive as I wanted to. And she definitely improved her game.
"At the beginning, she was making a lot of unforced errors, and in the third set she played unbelievable tennis. There wasn't much I could do."