Defending champion Karolina Pliskova survived a scare before beating Anastasia Pavlyuchenkova at the Nature Valley International but Heather Watson is out.
Pliskova, who has reached the final in each of the last two years, was the champion 12 months ago beating Caroline Wozniacki, and she did enough to remain on course to defend her title on the South Coast.
The Czech is seeded second and, having taken the first set, looked to be heading for a routine victory but Pavlyuchenkova had other ideas, storming to the second set before Pliskova composed herself to seal a 6-4 2-6 6-3 success.
Pliskova will face Barbora Strycova or Donna Vekic in the last 16 and could yet face a repeat of last year's final after top seed Wozniacki came through her match with Italy's Camila Giorgi - her first match of the grass-court season.
Giorgi took the first couple of games but was no match for the Dane thereafter who claimed the next six games in succession to wrap up the first before sealing a 6-2 6-3 victory.
Wozniacki could face a second-round showdown with Johanna Konta if the British No 1 beats Aleksandra Krunic in their second round encounter on Tuesday.
The news was not so good for the British No 2 as Watson went down to a three-set defeat to Kristina Mladenovic who battled back from losing the opener to seal a 6-7 7-5 6-3 victory, and a meeting with eighth seed Ashleigh Barty.
We will keep you up to date with all the news ahead of Wimbledon including our live blogs once the action gets underway on July 2.
Our next tennis action comes from the German Open in Hamburg. Watch the action live on Sky Sports Arena from Monday, July 23 from 10am.
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