Yeah, it's 4-5-1V, and also 4-3-3, but not flat, depends how you look at it. Busquets is the holding midfielder, he can be classed alongside Iniesta and Xavi, but plays slightly further back, and the wingers can push forward to join Messi as wide forwards.

How would it be a 4-2-3-1? Busquets is definitely behind both Iniesta and Xavi.