Who, in particular, do you think needs replacing?
I'd say you'd need a keeper, centreback, leftback and defensive mid. The players in these positions for you are generally a bit too weak. Obviously centreback and defensive mid you have djourou and song who are both young but i'd still give them more time to develop by getting some solid partners in.
NewPlayer
Sagna Vermaelen NewPlayer NewPlayer
Wilshere NewPlayer
Walcot Fabregas Nasri
Van Persie
That team looks quite tasty I think.