Canada's Denis Shapovalov said he was "incredibly ashamed and embarrassed" after he was defaulted for hitting the umpire with a ball - handing Great Britain Davis Cup victory in Ottawa.
The 17-year-old had just dropped serve to trail Kyle Edmund 6-3 6-4 2-1 when he angrily hit the ball out of court.
It struck French umpire Arnaud Gabas in the eye and a default followed.
"Luckily he was OK but obviously it's unacceptable behaviour from me," said Wimbledon junior champion Shapovalov.
"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.