British number four James Ward has suffered a surprise straight-sets defeat to Brydan Klein at the Aegon Surbiton Trophy.
Ward, who sits at number 108 in the world rankings, lost 6-2 6-4 to Klein, who was born in Australia but has represented Great Britain since 2013.
British number five Liam Broady also bowed out of the tournament after losing 6-7 6-3 6-0 to big-hitting American Ryan Harrison.
Daniel Cox, the British number eight, suffered a 6-3 7-6 defeat to Maxime Authom, but there was better news for Joshua Milton, who reached the quarter-finals of last week's Aegon Manchester Trophy.
Milton, who moved 36 places up the world rankings at the start of the week, dropped the opening set to Edward Corrie but advanced through to the last 16 after his opponent was forced to withdraw through injury
The 25-year-old will play Luke Saville in the second round, Klein will meet Frederik Nielsen, while David Rice, who progressed on Monday, faces a tough clash with Denis Kudla.