Do you follow Wolfsburg ALC? I actually haven't this year, but I still know that they had at least one coaching change mid-season - I've never been impressed by McClaren (possibly/probably a shift in tactics?), and got rid of their best couple of attacking players this year. There were also changes to the defense (at least Kjaer) that didn't go as well as anticipated.
You want to put the blame on Diego? What a crock of shit. When a team wins the Bundesliga, and a couple of years later is battling against relegation, there are obviously major internal issues. Diego's confidence was already in the shitter, and obviously joining a dysfunctional team like Wolfsburg is not conducive to a player regaining past form. The guy needs continuity in a stable, quality environment if he's going to rediscover his game.
We never should have sold the player after one season, the price we got for him was utterly stupid, and selling Krasic now would be a monumental error. Milos has qualities that can help this team moving forward - we just need to put some more quality pieces around him, get some better movement up front, support from the back, balance the field so we're not so damn predictable; he needs some more players he can regularly combine with, and continuity, which is absolutely necessary to develop some chemistry with his teammates.