Dayana Yastremska may still feature at the Australian Open as the Court of Arbitration for Sport (CAS) has started hearing an urgent appeal against her ban for a positive doping test.
The world No 29 was suspended earlier this month after the World Anti-Doping Agency (WADA) found a banned substance in an out-of-competition urine sample she submitted.
But she still travelled to Melbourne ahead of the Australian Open and is currently in 14-day quarantine after a passenger on her flight tested positive for Covid-19.
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The International Tennis Federation (ITF) had denied Yastremska's application to have the suspension lifted even as she was preparing to compete in at the Australian Open, which begins on February 8 in Melbourne.
"The CAS arbitration has commenced and the parties have agreed to an expedited procedure in order to enable a sole arbitrator to issue a final decision by February 3," CAS said in a statement.
Yastremska had denied using performance-enhancing drugs and said the positive test was the result of a "contamination event".
She wrote on Twitter: "I have never used any performance enhancing drugs or any prohibited substances I am astonished and under shock, particularly given that two weeks prior to this test, I tested negative at the WTA event in Linz.
"Only a very low concentration of mesterolone metabolite was detected in my urine. Given that low concentration and my negative test two weeks earlier, I have received scientific advice that the result is consistent with some form of contamination event.
"Due to the confidentiality of the proceedings, you will understand that I am not able to share any further information at this stage. However, I am currently working with my team and you can be assured that I am resolutely determined to do everything to clear my name."
Additional reporting by Reuters
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