Well, there is more to a war than simple fighting. Diplomacy and politics play just as big a role in all of this as the men on the ground killing the bad guys. General Abizaid is not going to be up on the diplomacy and politics as much as the VP.
Remember Muqtada al-Sadr? What ever happened to him? It was a combination of politics, diplomacy and some plain old firepower that marginalized him. All are needed. General Abizaid is a key figure in one of those ingredients. I am sure he is aware of what is happening on the other two fronts but I am also sure he is not 100% aware.