Former world number one tennis player Maria Sharapova has revealed she failed a drugs test at the Australian Open.
Nick Bollettieri, who is a former coach of the five-time Grand Slam tennis champion, said he was surprised by the news and believes she made an honest mistake.
The Russian, 28, tested positive for meldonium, a substance she has been taking since 2006 for health issues.
"It's a game-changer for life, not just for tennis," Bollettieri told the Today programme.
The International Tennis Federation said Sharapova would be provisionally suspended from 12 March.