I was looking at the results of Contador and noticed that in 2004 he had only one victory, and found that the reason for that was a disease called Cavernous hemangioma. From Wikipedia:
I have never heard about this before, which is strange as it is not dissimilar to Armstrong's story.Contador turned professional in 2003 for ONCE-Eroski. In his first year as a professional he won the eighth stage of the Tour de Pologne, an individual time trial. During the first stage of the 2004 Vuelta a Asturias he started to feel unwell, and after 40 kilometers he fell and went into convulsions. He had been suffering from headaches for several days beforehand and was diagnosed with a cerebral cavernoma, a congenital vascular disorder, for which he underwent risky surgery and a recovery to get back on his bike. As a result of the surgery, he has a scar that runs from one ear to the other over the top of his head. Contador started to train again at the end of 2004 and eight months after the surgery he won the fifth stage of the 2005 Tour Down Under racing for Liberty Seguros, as the team previously known as ONCE had become.