In my Wolfsburg game (well, Atletico madrid game now..) Barca placed Keita on transfer list and I said to myself - buy him ASAP! I bought him pretty easy (didn't demanded a large contract) and I played him as MC - Box to Box Mid'fielder. He is BRILLIANT!
If you have two in the MC, try using Keita as Box to Box MC, and Xavi as Advanced Playmaker (attack), and two Inside Forwards (AML and AMR), aswell as two strikers (left one deep lying, right one poacher, or try target man and deep lying forward). (DR and DL has to be full back, with support duty)
If that's the tactics (ofc there's team instructions which im not gonna post (not that i dont want to, but it's much of a writting) DL pass to ADV playmaker, he passes it to B2B (inthis case keita), and he make the assist to deep lying (or sometimes to poacher)
it works every time! :d