Tennis world number one Serena Williams says Maria Sharapova has been courageous in taking responsibility for her failed drugs test.

The Russian five-time grand slam winner is facing a suspension from the sport.

Sharapova puts the result down to medicine she has taken for years that includes a substance only banned in January of this year.

Williams says she was surprised and shocked by her rival's announcement last night.

"I think most people were happy that she was up front and very honest and showed a lot of courage to admit to what she had done and what she had neglected to look at. It's just taking the responsibility which she admitted she was willing to do and ready to do," said Williams.