It wouldn't surprise me - I think PED use (and I mean stuff like EPO, blood boosting, gene therapy, not just old fashioned injections) are rife in many sports.

If you can get such institutionalised doping in something like cycling or weighlifting, where they have very strict testing, just think what could be out there in siomething as unregulated as boxing or MMA

I also have dark suspicions about Novak Djokovic (allegedly)