Canada's Denis Shapovalov says he would not have been able to forgive himself if the umpire he hit in the eye with a ball had been seriously injured.
Shapovalov was fined $7,000 (£5,600) for his actions during a Davis Cup match with Great Britain's Kyle Edmund.
The 17-year-old trailed 6-3 6-4 2-1 when he struck the ball in anger and hit Arnaud Gabas, defaulting the match.
"I know how dangerous it can be to fire a ball," he told the BBC. "My first concern was that the referee was OK."
Speaking to BBC Radio 5 live Breakfast's Nicky Campbell, he added: "I turned over and saw the official bending down, holding his eye.