For what its worth(ie feck all) I think the reason that Rafa changed it was more to do with the way Newcastle play with very little width,with Shearer and Ameobi playing straight down the middle 95% of the time. If he had played 2 center halfs in an orthodox back four both our full backs would be sucked in to cover and would cut down on our attacking options from full back. By playing with a back 3 we always had a spare defender thus freeing up our two "wing backs". There are very few teams who play with two big center forwards so cant see Rafa using this system too often but its good to have it as an option and he may use it on Tuesday if he is expecting Brum to play with Heskey and Sutton.