No. 2: Kansas City Chiefs
The Chiefs are all set to play the 49ers in the Super Bowl, but outside of L'Jarius Sneed, there isn't much to brag about for the cornerback position. Adding a new body would be of the utmost importance, especially if Sneed leaves due to not receiving a contract extension (he more than likely will be retained, but just in case).
Also, there is a competitive reason to consider for the Chiefs, and that starts from within their own division and the moves that were made amongst all three teams this offseason.
The Raiders chose to retain Antonio Pierce, the Chargers went after Jim Harbaugh, and the Broncos still have Sean Payton and some draft capital that they didn't trade away. Kansas City shouldn't necessarily be afraid of the others catching up, but they still need to be cautious because there will be a year where the division isn't a cakewalk (it also happened to the Patriots).
The best thing to do is to fill the holes as quickly as possible if any exist. Mitchell would come in and, with a bit of coaching, can fill that hole with ease, and put yet another feather in the cap of general manager Brett Veach.