He should definitely go to a bigger club, he is not that young anymore and he should try himself on a bigger stage. I am not his biggest fan and I think he lacks some important things to become really good midfielder, but many average players with good set-up around them are considered better players than him even though he definitely has some special things in him not many players have.
I wouldn't mind if we tried to bring him here for decent price, he would probably cost us around what we payed for Fellaini, which isn't much in today's market, plus his wages shouldn't be high at all considering he is coming from Italy, so we could do much worse. At worst he can be a good squad option, and considering he didn't have some major problems with injuries and is fit most of the time(at least so far) he wouldn't be Phil Jones squad type of player, so he's definitely not a big risk.
He would improve us a lot technically, and bring something else to our play in final third with his creativity.
He is much better at free kicks than Memphis, Memphis only did it one year in Eredivisie, Pjanic does it regulary ever since he is on the scene, in French league, in Serie A, CL and on international level. And it's not just scoring goals, his crossing from set pieces is excellent. Just yesterday Bosnia scored against Spain from his excellent corner kick. That's definitely good thing to have in your team.
Though I don't doubt for a second that he will lose it if he joins us.
