World number one tennis star Serena Williams has praised the "courage" of her long-time opponent Maria Sharapova after the Russian admitted to failing a drug test.
The five-time Grand Slam champion announced on Monday that she tested positive for meldonium after losing to Williams in the Australian Open in January.
The substance, which Sharapova claimed she has been taken as prescribed medicine for the past 10 years, was included in the World Anti-Doping Agency's performance-enhancing drugs list at the start of 2016.
Sharapova, who will be provisionally suspended by the International Tennis Federation from March 12, is facing a four-year ban from competing.
When asked about the admission during a press conference previewing an exhibition match against Caroline Wozniacki at Madison Square Garden, Williams told reporters: "I think like everyone else, most people were surprised and shocked by Maria, but at the same time, I think most people were happy that she was upfront and very honest and showed a lot of courage to admit what she had done and what she had neglected to look at in terms of the list at the end of the year. I hope for the best for everyone in that situation."
Williams and Sharapova have gone head to head in top-flight tennis 21 times.
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