Great post mate. When we played 442 it was ok for Silva to be a wide player because he could drift inside and find space where he is so dangerous. Playing a 4231 however, he HAS to play in the middle for me. When he started on the right on Saturday, there was no space for him to drift in to - De Bruyne was already there.
I love De Bruyne as a player, but I think he is too direct to play at 10 for us. We need someone there who dictates play, an "out ball" that our defenders and midfielders can always look for which allows them to push out. Someone they can rely on to keep possession and bring others in to play. KDB's first thought is not to link up play, it's to head towards goal. We've needed a bit more of that mentality, but he's more suited to playing wide for us.
Playing Silva centrally also frees him up from having as much defensive responsibilities. In the first 25 minutes on Saturday he was often on the edge of our box, holding his man up, trying to win it back. He was doing his best, but I don't want him there, I want him further up the pitch doing what he does best!
I actually think the Newcastle goal was Silva's fault, he didn't track Winjagen's run. But I don't really blame Silva, he's a playmaking genius, I don't want him tracking runs in our box. I want him in essentially a free role, dictating the game from further up the pitch.