I wrote this in another thread, but it's more suited to here as it sums up my thoughts on him.
The way our team is set up, it's absolutely vital that the two number 8's make themselves available for a pass. That's how we build an attack, the back 4 and Fernandinho feeding the ball in to our number 8s (Silva and DeBruyne) high up the pitch who then slip in one of the wingers or forwards.
Players in this number 8 position are generally operating in very tight spaces with opposition players closing them down. They have to be comfortable receiving the ball under pressure and with little space. They have to constantly make themselves available to receive a pass. That takes real courage. Silva is the best I've ever seen at it, he always wants the ball, will always make himself available for a team mate, always offers an outlet. His touch and balance allows him to slip past opposition players who are tight against him, after he has received the ball.
DeBruyne perhaps isn't quite as comfortable receiving it in such tight spaces, so he wanders to where the space is, sometimes deep, sometimes wide, and he delivers undefendable balls from deeper. He works his arse off to create the space to make himself available to receive the ball.
Gundogan however, does neither of those things. When he is tightly marked, he doesn't demand the ball like Silva does, he doesn't work hard to create the space off the ball ball like DeBruyne does. He hides. I don't know if you go to the games, but you wouldn't see it on TV, but watch his movement when our back 4 or Fernandinho has the ball. He should be showing feet, offering an option, but he doesn't. He faces forwards with his back to the ball, not interested in making himself available.
He did this for the full 50 odd minutes he was on the other night. That's one of the reasons our tempo was so slow. There was only Silva offering himself as an outlet, Gundogan just wasn't interested. He didn't want the ball. I've heard both Pep and Fergurson say that most courageous thing you can do on a football pitch is always want the ball, even when things are going badly. Gundogan doesn't want the ball.