Maria Sharapova says her two-year ban for taking meldonium is harsh and unfair but former Wimbledon champion Pat Cash believes she got off lightly.

Sharapova plans to appeal the two-year ban handed down by the International Tennis Federation (ITF) for testing positive to the banned substance meldonium at the Australian Open in January.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 2 minutes 48 seconds 2 m 48 s Maria Sharapova says she'll appeal 2-year ban for doping ( David Taylor ) Download 5.1 MB

"I cannot accept an unfairly harsh two-year suspension," Sharapova wrote on Facebook.

Cash admitted he was surprised by the stance taken by the ITF and had expected a ban of about a year due to Sharapova's claims it was a genuine mistake.

But the Australian said the lengthy ban was likely to be a consequence of the ITF concluding that the Russian tennis star knew meldonium was a performance enhancing drug before being caught out by its recent addition to the banned list.

What is meldonium? Also known as Mildronate, it is used to treat angina and myocardial infarction

Also known as Mildronate, it is used to treat angina and myocardial infarction Manufactured and marketed by Latvian company Grindeks

Manufactured and marketed by Latvian company Grindeks Used in Russia and Lithuania, but not approved by USA's Food and Drug Administration Leading sports doctor Dr Peter Brukner gives the rundown on meldonium and what it does to your body.

"She clearly knew and her doctor [knew] that it was performance enhancing," Cash told ABC 702 Sydney.

"She'd been taking it for a long time. It's quite simply cheating, its a very special chemical and its very tough to get."

Cash said Sharapova could have been better advised by her management as to the change to the banned list but was informed by the Women's Tennis Association (WTA) of the update.

"She's made a mistake, but my gut feeling is if you're a professional athlete and you know you're taking a performance-enhancing drug, which clearly she was - then two years, I think she got off pretty lightly in that respect," he said.

The 1987 Wimbledon champion wonders how much meldonium assisted Sharapova's performance.

"How much does it help her get through those hot days in Australia, those long matches in the stinking heat of New York, or wherever else it happened to be," Cash asked.

"She's going to be able to recover much better than the other athletes. How many matches has this helped her win? It wasn't on the banned list but it was performance-enhancing.

"I think her career and reputation is absolutely shot to pieces."

Supporters and sponsor back Sharapova to return

Maria Sharapova revealed in March she had tested positive to meldonium. ( AFP: Robyn Beck )

Sharapova's sponsor Nike announced it would resume its partnership with the 29-year-old after the ITF said the doping offence had not been committed intentionally.

Her former coach Gabe Jaramillo has backed Sharapova to return to the game and said she did not know she was breaking the rules.

"I think two years is too long," he said.

"They tried to prove that she did it intentionally, that she went to a doctor, [that] she was trying to enhance the capacity but they were not able to prove that.

"I would bet that she will make it again, because she's not one to give up."

Cash is not so sure.

"It would be quite reasonable to expect her to pull up shop and say 'that's enough for me'."