On one hand, I would have to question why anyone would actually cheat at this point. It's one to have done it before, when the only risk you really ran was getting caught. Now, even if you don't get caught, you have people calling you a cheater regardless.
On the other hand, I might just buy that this guy started juicing so as to up his HR total by 15, or something totally legitimate-looking, that could easily net him a bigger contract without drawing any real suspicion. But once he started launching, he was all like, "This is fun," and kept going with it, deciding the presumption of guilt was worth it.