Nick Kyrgios retired with a left hip injury on the opening day of the Aegon Championships at Queen's, putting his Wimbledon prospects in doubt.
Kyrgios slipped while sidestepping along the baseline in game five of the first set of his match against Donald Young, landing awkwardly and aggravating an existing issue.
The Australian – seeded ninth – continued but he failed to convert two break points at 5-5 and after Young edged the tie-breaker 7-3, he called it a day ahead of the second set.
"I got the injections a couple weeks ago, and then I was in rehab for a couple of weeks and it settled down, and then on that fall I just felt sharp pain," Kyrgios said.
"So I felt pretty much everything I was feeling a month ago. It's not great at the moment. But we'll see."
Jo-Wilfried Tsonga eased past fellow Frenchman Adrian Mannarino 6-2 6-2 in 66 minutes, Tsonga seemingly relishing being back on grass after a difficult clay-court season that included a first-round exit at the French Open.
"For me it was really important to have a victory," said Tsonga. "On clay it was difficult, so it's good to be back and be able to play second round in Queen's."
Grigor Dimitrov made light work of Ryan Harrison 6-3 6-1 and Denis Shapovalov overcame Kyle Edmund 7-6 (7-4) 4-6 6-4, while Tomas Berdych found the going tough against Steve Darcis.
Seventh seed Berdych secured a crucial break when Darcis was looking to serve out the first set and got another to avoid a tie-break.
The Czech had to battle from behind in the second after opening with a drop of serve, but he rallied to complete a 7-5 6-3 victory.