Dayana Yastremska has been provisionally suspended after the World Anti-Doping Agency (WADA) found a banned substance in an out-of-competition urine sample, the International Tennis Federation (ITF) said on Thursday.
The 20-year-old Ukrainian has enjoyed a couple of positive years on the WTA circuit, winning her first three titles between October 2018 and May 2019, and reaching another final in Adelaide at the start of 2020.
A sample which uncovered the banned substance mesterolone was provided on November 24 and Yastremska was formally charged on December 22.
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"Yastremska was charged with an Anti-Doping Rule Violation under Article 2.1 of the Programme (presence of a Prohibited Substance in a Player's Sample) and was provisionally suspended with effect from Jan. 7," the ITF said.
The provisional suspension applies from January 7 and she still retains the right to appeal to the Chair of the Independent Tribunal. She is yet to exercise that right.
Yastremska has insisted upon her innocence, saying in a statement: "I am astonished and under shock, particularly given that two weeks prior to this test - on 9 November 2020 - I tested negative at the WTA event in Linz.
"Only a very low concentration of mesterolone metabolite was detected in my urine. Give that low concentration and given my negative test two weeks earlier, I have received scientific advice that the result is consistent with some form of contamination event."

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Yastremska went on to say that she is not able to provide further details at this time, but that she will keep working to prove her innocence.
Yastremska ended the 2020 season ranked 29th in the world.
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