It poisons the well for those of us who know better, though. First, defense is far more stable than offense. Dozier might hit three bombs in a night and drive in seven runs and then not hit another homer for three weeks. But Byron Buxton, while he may flub the occasional play, is not going to be 10mph slower while running down a flyball on any given night. And defense can't be influenced by the opposing pitcher, who can and will routinely shut down an offense. Second, there's the huge gap in data points. A starter, if healthy, only starts 32-ish games a season so we're already suffering from sufficient data points. Second, runs are much more rare than defensive putouts (something to the magnitude of 6-7x more rare per game than defensive putouts). He could have just as easily made the argument without making such an obviously flawed comparison. Defense doesn't slump but offense does on a very regular basis. If Posnanski can find me the defensive equivalent of a pitcher being on the receiving end of his offense posting a ten spot in five innings, I'd love to see it (and a single ten run outing is worth .33 run support over a full, healthy pitching season).