Experienced Australian rugby league centre Michael Jennings has said he is "completely shocked" after failing a drugs test and vowed to clear his name. The Parramatta Eels star, who has played for both Australia and Tonga, was provisionally suspended on Saturday after returning a positive A-sample for Ligandrol and Ibutamoren. Both are prohibited by the World Anti-Doping Agency. The 32-year-old has a right to have his B-sample analysed, but faces a potential career-ending four-year ban -- the standard penalty for athletes who test positive for anabolic agents. "I am totally against any form of cheating in sport and am completely shocked to find myself in this position," he said in a statement late Saturday. "I will do everything I can to clear my name." "I have dedicated the last 14 years of my life to playing in the NRL. I would never do anything to jeopardise my standards, my reputation, or the legacy I leave, especially for my son," he added. Ibutamoren is a growth hormone while Ligandrol helps build muscle. Australian relay world-record holder Shayna Jack also tested positive for Ligandrol ahead of last year's world swimming championships. She denied knowingly taking the drug and claimed the banned substance could have got into her system by contamination, with the case still ongoing. mp/qan