ok, first off, props to thiago to fessing up to what he did and it seems honest and if it really was for injury than i can see why he made the decision.
At the same time, wtf?! bro, why not pull out? back injuries are not something to try to hide and this does not justify knowingly cheating. Thiago should get punished, but since nobody can really prove without a doubt it was for injury and he did it with intentions to cheat and tried to hide it he should be looking at and aceept a punishment of a fine, suspension and the win being changed to a no contest.