Tennis star John McEnroe, famous for his on-court tantrums, has advised players to channel their anger into the game.
The former world number one, 53, famous for his "You cannot be serious" rant, was labelled Superbrat for his explosions of temper.
But he told the Radio Times: "Anger should be fairly straightforward. If you use that anger in a positive way, where you get yourself to try harder and dig deeper, it can be a good thing."
McEnroe made the comments before a line judge was injured on Sunday after tennis player David Nalbandian kicked an advertising hoarding.
Former world number one McEnroe said of his own outbursts: "It was not as controlled as I would have liked. Initially especially, the intensity and the energy that I let out in certain ways helped my tennis."
He added: "The fact that perhaps I thought I could get away with certain things doesn't mean that I did things on purpose. It just means that I was less afraid that I would get penalised if I did do something."
He said the wasted energy and anger became what he called "the lob of diminishing return".
The three-times Wimbledon champion turned commentator said that Scottish star Andy Murray could turn his emotions to his advantage.
He said anger used to increase his own intensity level, adding that if Murray could use his emotions in a way which would not hurt his game it would be a good thing.
But he said of Murray's chances of winning Wimbledon: "It's becoming more difficult ... It's not getting any easier."
McEnroe said attending anger management classes after retiring was "far more complicated" and added that he became more open to the idea of "perhaps getting help from other sources".