USADA's charges that Lance Armstrong took performance-enhancing drugs may have been based on 10 of the cyclist's teammates, who the agency claims would have testified against Armstrong. The seven-time Tour de France winner ended his fight against the charges on Thursday, which amounts to an admission of guilt in the eyes of USADA and the WADA.

In the wake of Lance Armstrong's decision to stop fighting USADA's charges, some have wondered what the agency had to support their allegations. Armstrong only once failed a drug test and it was for a substance prescribed by a doctor and therefore allowed, but athletes have been found guilty of doping before without a positive test and Armstrong was next on USADA's list.

USADA also said it had 10 former Armstrong teammates ready to testify against him. Other than suggesting they include Landis and Tyler Hamilton, both of whom have admitted to doping offenses, the agency has refused to say who they are or specifically what they would say.

The 10 teammates were reportedly going to testify that they witnessed Armstrong inject himself with banned substances. UCI, the sport's governing body, says that USADA will now have to explain their decision, which may or may not shed light on their case against Armstrong, what his teammates were ready to testify to and what other evidence they had in addition to the testimony.

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