That's because he is on a 1-3 team with a sub par Defense.
Here is one:
How do the Vikings have a sup par defense?!?! Ranked 1st in rush D for last couple years and definitely improving in their pass defense even without the big acquisition of M. Williams....He doesn't get enough cred I believe because this is going to be his break out year, not to many people know much about him yet.....He was injured in his first and had a pretty decent year last year....After this year and even at the end he will start getting some more credit!