Indian wrestler Narsingh Yadav was handed a four-year doping ban on Thursday after the World Anti-Doping Agency won its appeal against his earlier exoneration.
An Indian anti-doping disciplinary panel had ruled earlier this month that the wrestler was a victim of "sabotage", and cleared him to compete in Rio. Freestyle wrestling starts on Friday.
The freestyle wrestler had said his supplements and water had been sabotaged and lodged a police complaint against a junior wrestler accusing him of contaminating his food at the Sports Authority of India training centre in Sonepat.
WADA filed an urgent application before CAS to challenge the decision of NADA India to exonerate Yadav following two positive anti-doping tests in June and July.
"The CAS Panel did not accept the argument of the athlete that he was the victim of sabotage and noted that there was no evidence that he bore no fault, nor that the anti-doping rule violation was not intentional," CAS said, announcing a four-year period of ineligibility.