Pirlo was an amazing player back in the days. He still has qualities for sure, but his game has more flaws now due to his age. Chances are high that he'll be extremely limited if we don't provide a good cover next to him and if Vidal fails to play aggressive role and eats opponents' midfield. Our mid duo will be fragile against high paced teams too and 4-3-3 formation will terrorize ours as I think that's the weakest spot of 4-4-2. I'm not afraid of Pirlo losing the ball against aggressive play or high paced teams, but he will play it short and we'll be cut off out creative (and only creative) source from midfield. That being said, if Vidal gets to do his job well (not just well, but great) then Pirlo will have 3 meters of open space around him, which will be enough to provide excellent passes and control our whole play. I think he will get to play great against midtable teams but I don't think he'll be useful in hard matches. At some level we're lucky we're not in Europe because we'd get eaten I think. And eh, too bad we didn't keep Melo as I think 4-3-3 with Melo - Pirlo - Vidal was just perfect to have and we'd have much, much less weak spots open.