As graceful as Maria Sharapova might have been explaining her failed drug test, she didn't ingratiate herself to former tennis star Jennifer Capriati.

The 39-year-old, three-time Grand Slam champion went on a Twitter rant against both Sharapova and the ITF after Sharapova revealed she has been taking Meldonium that her doctor has prescribed for the last 10 years.

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Sharapova said she was taking the drug to combat a magnesium deficiency and because her family has a history of diabetes. The World Anti-Doping Agency added Meldonium to its list of banned substances this year, and the International Tennis Federation reported that Sharapova failed a drug test during the Australian Open on Jan. 26.

"Also known as mildronate, (Meldonium) is typically prescribed for heart failure patients in some parts of Europe," CBS News reported. "It treats ischemia, or lack of blood flow. But when taken by athletes, Meldonium may also help increase endurance performance, improve rehabilitation after exercise, protect against stress, and enhance the central nervous system, according to a 2015 study by German scientists."

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"Meldonium increases an athlete's endurance and exercise tolerance and it also reduces recovery time which is really important in high level athletes," said Dr. Robert Glatter, an emergency physician from New York. He added the drug is prescribed freely in Russia, Sharapova's home country.

And that enraged Capriati.

Capriati then got into it with some of the people objecting to her anger toward Sharapova.

At least the tweets reveal the passion Jennifer Capriati still has for the game, and the passion Maria Sharapova's fans have for her.

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