What his problem, at least according to pitch f/x was, was that he started throwing a two seam fastball and it killed him.
Go back to his first year and he got great results with his four seam fastball... add in the two-seamer, and bad things start to happen.
62.9% Four Seam Fastball
0.1% Intentional Walks
0.1% Pitch Outs
In 2008, Fangraphs had his fastball at 10.2 runs above average... from there, things go down the drain.
54.5% Four seam fastball
11.5% Two seam fastball
0.5% Intentional Walk
-4.8 runs below average on his fastball. Coincidence that his fastball starts to go south when he adds a two-seamer?
34.8% Two seam fastball
31.9% Four seam fastball
0.6% Intentional Walk
0.2% Pitch Out
-6.8 runs below average on his fastball. Two seam fastball is what he was featuring the most this year and he flat out sucked. I think what's been killing John Lannan is the fallacy that he was a sinker ball pitch... when in fact, he got by on his four seam fastball... all this time.