Pastore was a pretty good player when he played in serie a. But he needs to receive a free role.
One of his main strenghts was when he got space on counter attacks. THIS, is very interesting, considering we are the worst team in the world (/clarkson) when it comes to quick counters. Pastore could add a dimension there, and with Pirlo and Pogba we got players capable of quickly getting the ball towards him
Pirlo should know, back at Milan, he used to play in a 4-3-1-2 with Kaka in a simular role, and Milan was incredibly good on the counter back then. I recall them scoring at times where they cross the entire field in 2 or 3 passes and score.
Another thing with Pastore, is that he's pretty passive when not in possession when it comes to defending. But in our team, thats surprisingly excellent for the trequartista. Considering we got one of the forwards pressing as a mofo, and dat midfield, its actually very good to have 1 player allready moving into space to quickly receive the ball when winning it back.
Then again, that was before he went to PSG. I've barely seen a game of him, but i did see several compilations of him scoring or assiting counters, usually after getting the ball from verratti from 30 meters away.
But what would he cost ?