His stats this year back it up. Leading the league in takles (no small feat considering he's one of 2 mlb's in a 3-4), 4 sacks, 3 FF, 2 ints with one TD. If he stays at the top of the takles list and maybe gets one more sack or INT, I really think he has to be a finalist.
Especially scince this year there are no other clear favorites. No reduculous sack or pick numbers and there are no DT's that takes over games. I heard Jared Allen's name earlier on in the season but he has cooled off, and now two names that are being tossed around are Charles Woodson/Darren Sharper. They are both great players, and granted they are both on better, playoff bound teams, but neither lead the league in the stat they are known for (both have 8 ints, league leading is 9) and Willis's numbers are all around much more impressive.
Do I think Willis will win it? Probably not. Do I think he should. Of corse (but then again I'm a fan.) All I really hope is that he gets gets discussed as one of the main candidates so in future years when he anchors a top 5 defense and puts up numbers like these he actually will get it.