Tennis pros shocked over the news of Maria Sharapova's failed drug test but believe the sport needs to be clean.

While Maria Sharapova's fellow players were shocked by the Russian's announcement that she failed a drug test at the Australian Open, most of them felt the "huge mistake" could have been avoided.

World number three Agnieszka Radwanska of Poland described it as "a very sad day for tennis" but expressed the views of many by saying it was down to every player, via their doctor, to check whether prescribed medications were legal.

"I was actually in the locker room here watching with all the players what was going on," said Radwanska, one of the many top pros attending this week's tennis tournament in Indian Wells, Calif. "We're in shock, all of us. Nobody expected that for sure."

Five-time grand slam champion Sharapova tested positive for meldonium, which some researchers have linked to increased athletic performance and endurance, after failing, by her own admission, to realize that it had been outlawed since Jan. 1.

Men's world number five Rafael Nadal pointed to Sharapova's negligence while also hoping that the Russian had made an innocent mistake.

"Everybody can have mistakes," the Spanish left-hander said at Indian Wells. "I want to believe for sure that it is a mistake for Maria, she didn't want to do it."

"But it is obvious that it is negligence. The rules are like this. It is fair and now she must pay for it."

Sharapova, who faces a ban of up to four years pending an investigation by the International Tennis Federation, has received support by both world number ones, Novak Djokovic and Serena Williams.

"I obviously wish her all the best," Djokovic told TMZ Sports. "I've known her for a long time and I feel for her for what's happening. I just hope she gets out of this stronger."

Williams said, "It's just taking responsibility, which she admitted that she was willing to do and ready to do. She showed a lot of courage and a lot of heart. She's always shown courage and heart in everything she's done, and this is no different."