A .332/.397/.597 line is a peak year for a Hall of Fame career. He could be allowed to swim in a giant pool of syringes before every game like Scrooge McDuck and still not hit that well again.
Also, since batting average is part of slugging percentage, I don't think it's helpful to separate them for this sort of discussion. If 2012 defenders make fifteen extra plays than 2011 defenders on his singles over the six months of the season, that doesn't really say anything about Braun's chemical composition but it would reduce both his BA and his SLG.
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"Walleye, a lot of things are going to go wrong in your life that technically aren't your fault. Always remember that this doesn't make you any less of an idiot"