Dan Evans limped off court after retiring from his Erste Bank Open match against Frances Tiafoe with a serious-looking calf injury - four weeks before the Davis Cup Finals.
The British number two was leading 4-1 in the first round when he pulled up sharply at the baseline.
Evans, 33, looked forlorn as he received treatment and it soon became clear he would be unable to continue.
On Monday, Evans was named in Britain's team for next month's Davis Cup Finals.
Evans was instrumental in helping his nation qualify for the knockout stage of the men's team event and will be hoping the injury is not serious enough to rule him out.