Williams told a press conference in New York: "I think most people were surprised, but most people were happy that she was up front. It's just [about] taking responsibility, which she admitted she was willing to do.

"As Maria says, she's ready to take responsibility, and that takes a lot of courage and heart. She's always shown courage and heart (in tennis) and it's no different."

Williams refused to comment on how she felt knowing Sharapova had been taking meldonium - which was only banned in January this year but has never been ratified for use in the United States - since 2006.

The only two defeats suffered by Williams to Sharapova in their 21 career meetings both occurred in 2004 - before Sharapova said she started taking meldonium on medical grounds.

Williams added that she did not believe Sharapova's ban, which could effectively bring an end to her career although her camp hope "mitigating circumstances" will limit its length - will adversely affect the top of the women's game.

"I'm not concerned," Williams added. "There are a lot of great stars on the WTA Tour. We have a lot of young players, young US players doing really great. When the time comes someone will definitely step up and be that leader."

Former world number one and two-time grand slam finalist Caroline Wozniacki stressed the importance of checking substances after Sharapova insisted she had missed an e-mail declaring meldonium was now on the banned list.

"Any time we take any medicines we double and triple check," said Wozniacki. "Sometimes cough drops and nasal sprays can be on the (banned) list. As athletes we really make sure there's nothing in it that could (cause that situation)."

But despite Sharapova's admission she could still return to the circuit sooner than initially expected if she can prove she has a condition which requires the treatment she took.

Sharapova faces a ban of up to four years but former UK Sport anti-doping chief Michele Verroken says the 28-year-old Russian could receive some leniency if she can prove she needed to take the drug for medical purposes.

Verroken told BBC Radio Five Live: "We were all notified back in 2014 that it (meldonium) would be part of the monitoring programme. We were given notice end of September, beginning of October (2015) that the change to the list would include this now being a banned substance rather than just being monitored.

"Certainly for all the doctors that I work with, I know that they will have been checking the list and one hopes anyone advising athletes would make sure they are updating themselves specifically at that time in order to allow for the application for what they call a therapeutic-use exemption, if that's applicable, but if not, to change the treatment.

"Now the challenge facing Maria Sharapova and her team is to bring forward the diagnostic evidence that she has a condition that required the prescription of this treatment.

"But if she can actually prove that she may get some leniency from the disciplinary panel."

Sharapova says she accepts "full responsibility'' for her actions but former British number one Jo Durie believes the Russian might have expected more help from people around her.

Durie does not believe the former world number one is a drugs cheat either, saying it was a "very big mistake" that she is going to pay the price for. Durie said: "Everyone's shocked and it's just one big mistake isn't it from Maria and her team, who didn't pick this up.

"Maria has stood up and said ultimately that it's her responsibility, she's the athlete and she should check. But when you get to the top of your sport you are surrounded by a team of people who really should be advising you and checking and doing all these things.

Nick Bollettieri, whose academy Sharapova joined after moving from Russia to Florida at the age of seven, expressed sadness over her failed test and said he hoped she would soon be able to play again

He told BBC Radio 4: "I'll tell you why I'm surprised because, throughout her entire career, she's always been above board in everything.

"I don't think Maria Sharapova would continue doing something, especially being in the limelight, if there was something that she knew about. I would say that this is a mistake, but she accepts the consequences.

"I hope and pray that they will look back at the record she's established and hopefully they will give her the sanction but allow her to play again. Certainly she does not want to go out of tennis this way."