The one thing that Argentina missed at the worldcup, was a playmaker or player to connect midfield with attack.
Messi tried to fall back and do stuff , but every team that is not Belgium knows by now how do deal with that, and furthermore , it was too easy to cut off the supply to him.
Now, Argentina dont got a midfield general. Biglia is the only one, and that says enough cause he's mediocre (sorry ches).
But what if they would have brought Tevez along ?. If he would have played a simular role as he performs at juventus currently, with Aguero/Higuain and Messi in front of him, and giving Messi pretty much a free role there, that would have been quite something else.
One of THE best things about tevez is how he can drop off and link up with midfield, and is pretty difficult to get off the ball. This would have taken considerable workload from Messi's shoulders, who could just drift around Tevez and seak for space, or the combination with Tevez and Aguero.