(CBS) The Bears signed defensive end Jared Allen to a four-year contract Wednesday, a move that affords them versatility on the defensive line and has Bears fans, generally speaking, reacting optimistically about adding a dangerous pass rusher who has recorded an NFL-best 128.5 sacks since 2004, including 11.5 last season with the Vikings.

However, the advanced statistics of Pro Football Focus suggest that while Allen’s sack numbers were strong on the surface, his pass rushing skills actually declined last season. Allen, who will turn 32 next month, recorded career-worst pass rushing and overall grades, posting negative marks in both categories.

The first chart below shows how Allen’s performance declined noticeably last season, while the second one shows his game-by-game performance. Click on the embedded tweets to enlarge them.