Nike, TAG Heuer, and Porsche have announced that they are dropping Russian tennis star Maria Sharapova after her surprise confession Monday that she had failed a drug test for the Australian Open in January.

Monday, Sharapova — who is believed to be the highest paid female athlete in the world — announced in a press conference that she had been taking the drug meldonium for about 10 years to help her with various health issues. The drug was only added to the World Anti-Doping Agency ban list in December, a development Sharapova said she had simply failed to notice before taking a doping test for the Australian Open.

"I take great responsibility and professionalism in my job, and I made a huge mistake," Sharapova told reporters Monday. "I let my fans down. I let the sport down that I've been playing since the age of 4, that I love so deeply."

The tennis star now faces a potentially lengthy ban — possibly two to four years — by the International Tennis Federation, a ban which could prevent her from competing at the Rio de Janeiro Olympics.

Not long after her press conference, Nike issued a statement announcing it had suspended its contract with the star.

"We are saddened and surprised by the news about Maria Sharapova," read the statement. "We have decided to suspend our relationship with Maria while the investigation continues. We will continue to monitor the situation."

TAG Heuer and Porsche issued statements of their own, both explaining that they were suspending their negotiations for contract renewals with Sharapova until more evidence came to light.

Meldonium is a little-known drug that promotes blood flow, increasing oxygen intake and aiding endurance. The Latvian company Grindeks, which produces the drug, says it is usually only prescribed for four to six weeks of treatment, suggesting that it is highly unusual to use for an extended period of time, as Sharapova said she had done.

"Depending on the patient's health condition, treatment course of meldonium preparations may vary from four to six weeks," Grindeks told the Associated Press Tuesday. "Treatment course can be repeated twice or thrice a year. Only physicians can follow and evaluate patient's health condition and state whether the patient should use meldonium for a longer period of time."

How much will the dropped sponsorships hurt Sharapova? According to ESPN, she's made over $36 million in her 35 career single titles and Forbes estimated in 2015 that her sponsorship and business earnings approached $30 million. In other words, she'll be just fine.

​Here's video from the press conference Sharapova held in Los Angeles Monday, March 7 to announce her failed PED test (via ESPN):