Former tennis world number one Maria Sharapova said last night that she failed a drug test at the Australian Open due to a substance she has been taking the last 10 years for health issues.

The 28-year-old Russian, a five-times grand slam champion, tested positive for meldonium, which is used to treat diabetes and low magnesium, and was only banned by the World Anti-Doping Agency as of Jan. 1.

“I made a huge mistake. I let my fans down and I let the sport down. I have been playing since the age of four a sport that I love so deeply,” Sharapova told a news conference in Los Angeles yesterday.

“I know that with this I face consequences and I don’t want to end my career this way. I really hope that I will be given another chance to play this game.”

The stunning news came a day after Sharapova’s management team said she was going to make a “major announcement,” which had many speculating that she was going to announce her retirement from professional tennis.

Sharapova, who has struggled with a series of injuries in recent years, has not competed since she lost to Serena Williams in the quarter-finals of the Australian Open in January.

“I was first given the substance back in 2006. I had several health issues going on at the time,” said Sharapova.

“I was getting sick very often and I had a deficiency in magnesium and a family history of diabetes, and there were signs of diabetes. That is one of the medications, along with others, that I received.”