I don't get why we do this... it's an entire season and months are just arbitrary intervals of time. I think you could do less arbitrary intervals and have the point stand. Pena wasn't a crappy hitter all year, or even most of the year. It was two extreme slumps that pulled down his numbers, which is consistent with his BABIP for believing that 2010 was more fluke than decline. True enough, but I still don't understand what finding periods of time that dragged his overall numbers down tells us about anything. Especially when the periods of time are separate... if it was a bad first two months or something like that, I might get that a little more (that would likely lead me to speculate that the improvement less to do with bad luck and more to do with turning a corner performance-wise). But picking out two slumps that basically made his numbers crappy... I'm not really sure what to make of that other than I'd guess that most hitters who have bad years similarly have periods of both good and bad, with the bad outweighing the good. Granted, in Pena's case the differences between said periods are pretty extreme.