The chart above reflects Pena's batting average over rolling periods of 40 AB since he joined the Rays in 2007 through game 2 of the Angels series. You'll notice while he is hitting new lows, almost every single low mark has come with a spike in the percentage of lefties faced over the same period. This is true of the past few weeks as well.
However, we can also break it down in Rolling 40 AB periods by split (Click on Image to Enlarge):
Carlos Pena vs RHP
And Carlos Pena vs LHP:
Surprisingly Pena is testing his three year low vs. right-handed pitching at about .100 while hovering slightly below the middle against lefties. The biggest issue has been the perfect storm of struggling against each hand at the same time.The long term trend appears to be more severe versus righties. Pat Burrell can surely sympathize.
I have no definitive conclusions to offer based on these nifty charts but am curious to hear the community's thoughts.