Caster Semenya has been unfairly targeted by new rules around testosterone levels proposed by athletics' world governing body, according to 18-time tennis grand slam singles champion Martina Navratilova.
South African track star Semenya is challenging a proposal by the IAAF to limit testosterone levels in female athletes between 400 metres and a mile.
Semenya has a condition called hyperandrogenism which means her testosterone levels are naturally elevated, and the IAAF's proposals would require to her to take medication to reduce those levels.
The case is set to begin at the Court of Arbitration for Sport on Monday, with a judgement expected before the end of March.
Navratilova wrote in the Sunday Times: "Leaving out sprints and longer distances seems to me to be a clear case of discrimination by targeting Semenya.
"And can it be right to order athletes to take medication? What if the long-term effects proved harmful?
"Semenya's case will come up tomorrow before the Court of Arbitration for Sport. It is expected to last a week and the outcome is expected by 29 March. I hope she wins."