Peru captain and former Bayern Munich and Hamburg forward Paolo Guerrero will miss the World Cup in Russia. He was recently handed a one-year ban after he tested positive for performance-enhancing drugs, including cocaine. Guerrero claims he's innocent and that the result stemmed from a tea he was taking to offset flu symptoms, which was contaminated.

Dieter Baumann, German 5000-meter Olympic champion of 1992, later tested positive for nandrolone and was banned for two years in 1999, causing him to miss the 2000 Sydney Olympics. He argued that someone had contaminated his toothpaste. He came back in 2002, at the age of 37, to win silver over 10,000 meters at the European Championships in Munich.

Canada's Ross Rebagliati was the first snowboarding gold medallist in Olympic history. Hours after his win at 1998 Winter Games in Nagano, he was disqualified after THC - the active ingredient in cannabis - was found in his system. The decision was later overturned. Regbagliati insisted that the positive test was the result of second-hand smoke, but in 2013 he started a medical-marijuana business.

In the first known doping incident, coaches pumped a dangerous mix of strychnine and pure egg whites into American runner Thomas Hicks before his marathon at the 1904 St. Louis Olympics. In the absence of guidelines at the time, he was declared the winner of the race - even after collapsing at the finishing line and hallucinating for hours.

Dennis Mitchell (second from right) won Olympic relay gold for the USA at the Barcelona Olympics in 1992. Six years later, tests found he had illegally high levels of testosterone. His claims that he'd had "five bottles of beer and sex with his wife at least four times" was, somewhat surprisingly, accepted by the US Track and Field authorities, but not by the IAAF.

Highly-decorated Norwegian skiier Therese Johaug tested positive for an anabolic steriod last year and claimed that this was caused by the application of a lip balm. She received an 18-month ban that will rule her out of the Winter Olympics in February. The team doctor who gave her the balm resigned soon after.

Ekaterini Thanou and her training partner Konstantinos Kenteris failed to attend a drugs test on the eve of the Athens 2004 Summer Olympics. Later that day they were hospitalized, claiming they’d had a motorcycle accident. They withdrew from the Games, and investigators ruled the accident had been staged and they were criminally charged with making false statements to authorities.

Born as Heidi, Krieger was a female shot putter for East Germany at the height of the Cold War. Communist officials fed Krieger with staggering amounts of steroids, altering her appearance. Krieger began to publicly identify as transgender and later opted to have gender reassignment surgery, becoming Andreas.

Australian cricketer Shane Warne, widely considered one of the greatest to have played the game, received a one-year ban in 2003, missing the Cricket World Cup after testing positive for a diuretic. Warne said his mother had given him a substance to help "get rid of his double chin" when he struggled with weight issues.