Not sure if this has popped up in the comments somewhere already, but it appears our boy Amobi has been playing with a "high ankle sprain" for some time now. This is according to Kuharsky's blog.
In some respects, this would be similar to Mario's first year: playing through an injury that stunted (at least stat wise) his growth as a player.
I've not been willing to start voicing my skepticism about Amobi based on his play this year. He's younger than a lot of incoming rookies will be this year and has a lot of room to develop. The injury would go a long way toward explaining some of his troubles this season.