Britain’s Kyle Edmund went out of the Citi Open in Washington with a three-set defeat by Bulgarian fourth seed Grigor Dimitrov in round two.
Dimitrov won 7-5 4-6 6-3 and next faces Russian Daniil Medvedev, who beat Steve Johnson of the US 3-6 6-4 7-6 (7-1).
Edmund, 22, had been hoping to build on his run to the semi-finals of the Atlanta Open last week.
Australian 10th seed Nick Kyrgios again succumbed to injury in his first match since retiring at Wimbledon last month.
Kyrgios trailed world number 106 Tennys Sandgren of the US 6-3 3-0 when he retired with a right shoulder injury.
“Just struggling, mentally, physically,” said the 22-year-old.
Canadian third seed Milos Raonic needed two tie-breaks to see off Frenchman Nicolas Mahut 7-6 (7-2) 7-6 (10-8), while compatriot Eugenie Bouchard beat American eighth seed Christina McHale 7-6 (8-6) 6-0 in the first round of the women’s event.