Unfortunately Mathieu's agent did a great job on that deal, and Keim got fleeced. Can't get out of it next year. Another thing to consider is that - no matter how bad he plays - the vast majority of fans loves the Badger, as well as national media. Wouldn't surprise me if he is our 2nd most sold jersey after Fitz. Actually I think he is by a wide margin. He will be a Cardinal next year, like it or not.
As far as his play goes, he shouldn't cover the slot anymore. He lost the quickness you need for the slot which allows the WR too much seperation. They should move him back to centerfield full-time where his instincts can take over. Mathieu dropped a pick last game from the high safety spot, but made a great read to jump that pass.
Or another option, since we struggle at CB2 anyway, try him on the outside where you don't need to have the quickness like in the slot. It's really much tougher to play in the slot with so many different directions a WR can take from there. On the outside you can position yourself to take away half of the WR's possible release patterns, depending on what defensive scheme is called. Tramon Williams is so much older than a starting CB should be, but he is great at aligning presnap so that the WR has just one way to go. Instinct player, just like Mathieu. Maybe he can teach him a thing or two.
At least we got Baker who seems to be what Mathieu should've been for us.