British pair Steph Slater and Jack Thomas have been forced to pull out of the IPC Swimming World Championships in Glasgow next month.
Slater, 24, who was a talented able-bodied swimmer before suffering nerve damage, has not recovered from surgery on a hip problem earlier this year.
Welsh swimmer Thomas, 20, has suffered a wrist injury.
The pair join Paralympic champion Jonathan Fox on the sidelines after he was ruled out with a shoulder problem.
Both Slater, who won seven golds at last year's IPC European Championships in Eindhoven, and Thomas have expressed their disappointment at missing out on the event which runs from 13-19 July at Tollcross International Swimming Centre.
"I have been working really hard to get back to full fitness but Glasgow came too soon for me to be at my best," said Slater.
Thomas added: "Unfortunately I just won't be fit enough to race like I would want to. I really want to compete in Rio and I will do everything I can to make sure I can get there."