World number three Agnieszka Radwanska was knocked out of the Aegon Classic in Birmingham as American Coco Vandeweghe secured a hard-fought 7-5 4-6 6-3 win.
The Polish top seed had won all four of her previous matches between the pair.
British number one Johanna Konta’s match against Misaki Doi was delayed until Thursday by wet weather.
Naomi Broady and Tara Moore – the British numbers three and four – lost their matches against Daria Gavrilova and Tamira Paszek respectively.
Former Wimbledon finalist Eugenie Bouchard’s poor form continued as she lost to Latvian world number 82 Anastasija Sevastova in Mallorca.
The 22-year-old Canadian, who lost to Petra Kvitova in the 2014 final at the All England Club, has only been beyond the third round in two of the 13 tournaments she has played this year.
Subscribe to the BBC Sport newsletter to get our pick of news, features and video sent to your inbox.