As much as we all would love to add a player like Nnamdi to the Jets defense, problem is, so does everyone else. Although Nnamdi is, bar none, the most coveted free agent of 2011, there are a lot of really good players that may not be of his stature that would do wonders for a lot of teams. But one player, in particular, stands out as an excellent fit for the Jets:
Eric Weddle.
A 2007 Charger draft pick, Weddle is extremely versatile, can play the run. He's smart, but still has great range and coverage skills. He's like Jimmy Leonhard but with a lot more natural talent.
Rex's system (among a growing number of defenses in the NFL) require versatile safeties - unlike 10 years ago, when the SS would play the run and the FS would play the pass. Safeties are now required to play a lot more man to man, and the Jets were often burned by their lack of talent in the back of the secondary. A combination of Weddle and Leonhard would be like having Kerry Rhodes back, except Weddle will lay the wood (and he's probably not too interested in starring in a Hollywood movie anytime soon).
The FS spot is still in flux, and although Brodney Pool really came along in the Playoffs, he is a free agent. Weddle would be a massive upgrade at the position.
The real question now is how much money will he take away from signing other guys. He obviously won't command Nnamdi numbers, but getting a safety of his caliber entering his prime won't be cheap. He'll probably cost as much as some like Cromartie or at least somewhere in that ballpark.