Whilst we do need to strengthen in midfield, Silva is getting older and has been relied upon so much by City since he arrived. He's a player the opposition know they need to man mark if they want to beat us and now we've added Sterling it means we're an even bigger threat. De Bruyne has the potential to add the creativity we sometimes have lacked and fill in for Silva over the long term. Ideally they can play together for several seasons but once Merlin is gone, we'll have someone to fill that role (though I can't imagine anyone doing it quite like Silva does). It's still a signing that we very much need.
When we get Barcelona in the CL what does everyone look at? How will our defence cope with Messi, Neymar and Suarez? Last season they were only really worried about Aguero and Silva and that meant they could commit a few players further forward and hope to contain those two.
If we instead have a side with Aguero, Silva, Sterling and De Bruyne they then have a lot more to deal with and if Alves decides he wants to get forward so be it, he'll wish he hadn't when the ball gets to one of those players. We're an entirely different proposition. If we sign Pogba as well then we can also compete in the midfield battle and look to run the game a little better. We close the gap considerably to the likes of Real, Barca and Bayern with these two additions. Without them we're likely to play Navas or Nasri... not quite the same proposition.
