Tennis legend John McEnroe has doubts over Maria Sharapova's claims that she was unaware that meldonium had been added to a list of banned substances.
Former world No. 1 Sharapova sent shockwaves through tennis last week when she announced that she had failed a drug test at this year's Australian Open.
SHARAPOVA: The ugly truths | Recklessness does no favors | Photos
The Russian said that she had been taking meldonium for the past 10 years for medical reasons and did not know that the World Anti-Doping Agency had prohibited its use in January.