Five-time Grand Slam tennis champion Maria Sharapova has called on Philadelphia-headquartered firm Fox Rothschild to represent her as she appeals a two-year ban for doping, while Bird & Bird has been mandated by the International Tennis Federation (ITF).

The former top-ranked Russian tennis star was handed the suspension by the ITF last week for an unintentional anti-doping violation earlier this year.

But Sharapova is now appealing the decision to the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland.

Bird & Bird head of sport Jonathan Taylor and associate Lauren Page are acting for the ITF on the case, while John Haggerty, co-chair of Fox Rothschild's litigation department is representing Sharapova.

Haggerty said: "The appeal will be filed immediately and we expect that it will be heard in the next couple of months." Haggerty, based in the firm's Philadelphia headquarters and nearby Warrington, Pennsylvania, has represented Sharapova for nearly a decade.

Haggerty said he initially secured the high-grossing athlete as a client by working on behalf of Sharapova's agency IMG Worldwide, which was sold in late 2013 to rival William Morris Entertainment.

Sharapova – who has been ranked by Forbes as the world's highest paid female athlete for the past 11 years – ran into trouble back in January when she failed a drug test at The Australian Open.

In March, the tennis star announced she had tested positive for meldonium – banned by the World Anti-Doping Agency from 1 January this year. She said she had been taking the drug, prescribed to her by a family doctor and which she knew by its alternative name Mildronate, for ten years. Sharapova said she took "full responsibility" for the failed test, adding that she didn't realise the substance she had been taking for a magnesium deficiency and a family history of diabetes had been banned.

"We were very pleased that the tribunal [appointed by the ITF] found that Maria did not intentionally violate anti-doping rules, which was critically important to her," said Haggerty, noting that his client has the "highest integrity".

Haggerty also added that Sharapova has "played the game of tennis the right way and worked extremely hard [to] become a top-five player [and] come back from serious injuries".

Haggerty, who joined Fox Rothschild in 2009 from Ulmer & Berne, acknowledged it has been a "challenging process" for Sharapova to be associated with athletes that have used performance-enhancing drugs.

The Fox Rothschild litigator said he was pleased that the three-member tribunal backdated Sharapova's suspension to January in recognition of her admitting her unintentional violation immediately.

At the same time, Haggerty said he and his client were disappointed that the tribunal ignored several "mitigating factors" and imposed a suspension of two years.

"The contravention of the anti-doping rules was not intentional as [Sharapova] did not appreciate that Mildronate contained a substance prohibited from 1 January 2016," wrote the tribunal in its 6 June ruling. "However she does bear sole responsibility for the contravention, and very significant fault, in failing to take any steps to check whether the continued use of this medicine was permissible. If she had not concealed her use of Mildronate from the anti-doping authorities, members of her own support team and the doctors whom she consulted, but had [instead] sought advice, then the contravention would have been avoided. She is the sole author of her own misfortune."

"We always knew this would be a two-step process," said Haggerty, who added that he and his team at Fox Rothschild are primed for the appeal before CAS in Switzerland.

While the tribunal that imposed the two-year suspension was selected entirely by the ITF, Haggerty noted that the tribunal for the CAS appeal should be more neutral. Sharapova will select one member of the new CAS tribunal, a second will be nominated by the ITF and a third by CAS, he explained.

"We have the ability to reduce her sentence to as low as time served," Haggerty said. "We'll have to see how CAS rules to see if that becomes a reality."