Welshman David Greene has withdrawn from the Great Britain team for this weekend's Spar European Cup in Munich.
Greene has shown encouraging early-season form
The 21-year-old 400m hurdler has failed to shake off an ankle injury, and has been replaced by England's Ben Carne.
"I've got a slightly inflamed tendon which has prevented me from running," Greene, from Llanelli, told BBC Sport.
"The physio had told me I would be OK for this weekend, but sadly it hasn't healed as quickly as I would have liked so unfortunately I've had to withdraw."
With British number one Rhys Williams injured, Greene was selected for the GB team after running the seventh fastest time in Europe this season.
His time of 50.02 seconds three weeks ago was just over a tenth of a second outside his personal best.
But Greene has been unable to run since because of the injury, and has been forced to conceded defeat in his battle to be fully fit for Germany.
"I have been running some fast times and my training has been going great," Greene added.
"I was really looking forward to running in a fast race against some top some top quality opposition, so it's a big shame.
"But there's no point taking any unnecessary risks with the injury, hopefully I'll have many more opportunities to run for Great Britain."
Greene will now turn his attention to preparing for the European Under-23 Championships in Debrecen, Hungary on 12-15 July.
The former European junior silver medallist says he is targeting a gold medal, and then wants to secure his place in the GB team for the World Championships in Japan at the end of August.