Anyone comparing Witsel to Hernanes is being silly. He's clearly a decent player. I actually think he will be a more physical player under Allegri, and he will grow here because he's still at a decent age. A lot of his perception comes down to the time he's spent in Russia, if he was still at Benfica, a lot of people here would view this move differently. I think i would've been more excited with Herrera, but Allegri will bring the best out of this guy, and his best maybe good enough to plug the gap we are currently experiencing in the middle of the park.
