I am just surprised it took a normally sensible poster like you ages to come to terms with that. I have said it all along, we don't play well with a midfield two against decent to good opposition. The thing is, given the calibre of players we have, the only way to play with a midfield two is if we had a monster like Essien patrolling the midfield alongside a tactically disciplined and creative player like Carrick.
However we can still have an effective midfield even with the options we have but we just need to play an extra man in midfield. What is even more impressive is that we never play with a "sitting" defensive midfielder when we employ a midfield three, we usually have a deep laying playmaker in Carrick (recall his outstanding performance at the San Zero), one designated "hunter" (A player who will run around putting pressure on the opposition usually Fletcher or Hargreaves), and a "driver" (Dribblers like Giggs and Anderson).
We have been near unplayable in midfield in the times that we have played with a midfield three. Our attackers have usually been freed from any defensive duties and allowed to express themselves in the best way possible in the attacking third.
We have gotten used to 4-4-2 but put it simply with the players we have, we won't be able to play 4-4-2 against quality opposition.