In a news conference Monday in Los Angeles
, Sharapova said she tested positive for meldonium, an anti-ischemic drug
the Russian tennis star claimed she had used since 2006 that only became a banned substance this January.
The five-time grand slam champion -- the world's richest female athlete -- didn't read an email that revealed the 2016 drug list, she added, and that was the reason she continued to take it.
A provisional suspension begins Saturday, pending determination of the case, with first-time offender Sharapova facing a ban of four years. It likely would drop to two years or less if anti-doping officials find Sharapova didn't intentionally take the drug to enhance performance.
Her revelation surprised the tennis world, not only because the 28-year-old is known as one of the most professional players around, but because in the overwhelming majority of incidents when players fail a test and are initially notified, they keep it quiet.
"Ordinarily in these cases, the athlete is either disputing that the substance was in the body, that the samples weren't handled correctly, that there's some sort of explanation that absolves them entirely," Steven Thompson, a trial lawyer with Chicago-based Nixon Peabody, told CNN.
"She doesn't take that position. She's not saying this was something someone slipped into a water bottle, or anything like that.
"Her position is, as I understand it, she did take this as a prescribed drug product for many years, and unfortunately didn't realize that it had gone on the banned list. It's not an excuse, but it's a reason that may have an impact on the ultimate outcome."
Another factor that may help Sharapova, Thompson said, is inconsistent wording in the World Anti-Doping Agency's prohibited list.
Sharapova knew meldonium by another name, mildronate, and when WADA announced in September a set of substances that were to be added to the 2016 list, it used both names. "Meldonium" was immediately followed by "mildronate" in parentheses.
When the official list was released this year, only meldonium was utilized.
"There may be some allowance for this particular set of circumstances and that may be considered something that could be a mitigating factor," said Thompson, even though Sharapova's lawyer, John Haggerty, told CNN this week that no one in Sharapova's entourage consulted the 2016 list.
"I think it's an argument they will make and it could have some impact on the ultimate decision on the length of the penalty."
WADA spokesman Ben Nichols stood by his agency's protocols.
"We give the scientific names of substances because different products around the world can be called by different names, so we give the scientific names of the particular substance that is banned," he told CNN. "And that's the way the list has been created over the years. Expert analysis from scientists.
"And then of course it's up to the sports and the national anti-doping agencies to communicate those changes to their athletes as they see fit. We believe it's the right process that's been carried out over the years."
Sharapova should 'pay'
Serena Williams, a 21-time grand slam champion, praised her bitter rival for having "the courage" to come clean but former men's No. 1 Rafael Nadal was harsher, telling reporters ahead of this week's BNP Paribas Open in Indian Wells, California that Sharapova should "pay" for her error
if she was deemed to have been negligent.
Haggerty said Sharapova has taken 500 milligrams of meldonium "on a regular basis" for 10 years, one of several medications used to treat various ailments.
The drug's inventor Ilvar Kalvins, meanwhile, told CNN that athletes who train at high levels could suffer heart attacks if they suddenly stop using the drug, which was first manufactured 32 years ago and used by the Soviet military in the Afghan war of the 1980s.