Serena Williams, the top-ranked player in women’s tennis, said on Tuesday she was shocked to hear her friend and fellow tennis star Maria Sharapova had failed a drug test, but she commended Sharapova for showing courage in taking responsibility.

“As Maria said, she’s ready to take full responsibility and I think that showed a lot of courage and a lot of heart,” Williams told reporters at a briefing ahead of a match she will play on Tuesday night in New York.