What does jump out is a major decrease in fastball effectiveness. For his career, including the last two disappointing seasons, Lackey's fastball is about average (0.05 runs saved per 100 fastballs). However, in 2011 in particular, it has been horrendous (-1.71 runs saved per 100 pitches). Lackey is still sitting right around 91 with his fastball, so what gives?
The horizontal movement is about the same, but there is a massive decrease in the vertical movement of his fastball, based on PitchFX data. For the five seasons (including the partial 2011 season) that PitchFX data is available, there is an extremely tight correlation between the vertical movement Lackey's fastball and its effectiveness. In fact, the variation in fastball vertical movement explains 82.6% of the variability (R^2) in his fastball effectiveness! That's a damn good fit for a handful of points. It'd be even tighter, except his fastball has been so unbelievably horrendous in 2011 it makes a linear fit difficult. Fastball vertical movement is often described as "explosiveness". Despite what an announcer says, a fastball doesn't rise, but explosive ones don't drop as much as gravity would otherwise, thanks to spin.
Interesting side note: Lackey throws curveballs 20% of the time overall. However, when he's behind in the count is seems to be his go to pitch. In 1-0, 2-0, 3-1, and 3-2 counts he throws them 30-40% of the time, perhaps some issues have to do with predictability and pitch selection.
It isn't just Lackey's fastball that seems to be losing movement. Compared to 2009, his last season with the Angels, all three of his major pitches (fastball, curveball, and slider) have lost both vertical and horizontal movement, in inches (2009 points are hollow, 2011 are filled). On the plot shown they're moving towards the origin at the point 0,0, which would be a perfectly straight pitch. Again, the velocities are unchanged, but movement is key for any pitcher's effectiveness. Unfortunately, this doesn't seem like an easy fix. If it were one pitch I might think something was off mechanically or he was tipping, but everything across the board indicates that Lackey is in decline. Granted, that's probably not a surprise given that he now holds the leagues worst ERA, but it is a very scary thought given that the Red Sox have about $56 million tied up in Lackey through the end of the 2014 season.