Kovacic would be a bit underwhelming if this deal goes through. He has the potential no doubt, but it's a bit premature to classify him in the Dybala and Pogba category just yet. If he does come here he might find the right environment to grow and the right players around him, but if we are to make a statement of intent, I'd go with Pjanic, Isco or Goetze. In terms of just pure value for money and immediacy of impact, there is nobody better than Mascherano as an opportunity ,if it exists, this mercato.
Kovacic on the whole has a very similar feel to the Morata deal, when Alvaro came here first. Ability and potential went on to become a clutch, breakthrough star, but I think for it to happen for Kovacic we would need a lot of variables to fall into place, starting with how he's deployed in the formation of choice, followed by the 4312.