Teenager Denis Shapovalov defaulted a Davis Cup tie against Great Britain when a ball he smacked in frustration hit umpire Arnaud Gabas in the eye.
Already two sets up, Briton Kyle Edmund broke for 2-1 lead in set three and, on losing the point, Shapovalov thumped a ball away in frustration.
The ball smashed straight into umpire Gabas, whose left eye was badly swollen and had to be iced after the impact.
Shapovalov, 17, was distraught after the incident and apologised profusely while Gabas was given ice, while TV pictures showed his left eye badly swollen.
An emotional Shapovalov, who was playing in only his second Davis Cup tie, said: "I feel incredibly ashamed and embarrassed and I just feel awful for letting my team down, for letting my country down, for acting in a way that I
would never want to act.
"I can promise that's the last time I will do anything like that. I'm going to learn from this and try to move past it."