If they haven't been snapped up yet, what about, Kompany, Vanden Borre or Freddy Guarin (not sure if he'll get a work permit though)? Or there's the one that Cody found, David Bystron...even though he's a MC he has all the qualities of a good DMC. If you want to spend a bit more, there's Mascherano, David Pizzaro (although he's not great at tackling), Demechelis, Blasi, Pedretti etc. You might want to check out the Defensive Player Guide sticky too.
If you're Chelsea then none of these cheap ass options will do, you need a superstar. I suggest using Parker as a temporary stop gap and then when you get your next boost of money look for a superstar like Xabi Alonso or Gerrard. Alonso has a 30 Million Euro release clause, but he won't leave Liverpool usually for a year. I don't know what Gerrard will cost you, but you'll probably have to save up or spend all of your starting funds on him.
Those are my two suggestions as I don't think Arse will sell Viera for any amount of money.
Essien's an AM RC in the game. I guess you could try to retrain him to be a DM as his tackling is good (not sure if it's possible and how long it'd take though) but it just seems like too much effort to me.