Fernandinho is not a ball winner, he is an excellent all-around central midfielder. Chelsea play a totally different style than we do. When City bought Fernando, a pure ball-winner, he looked out of his element and contributed to their relatively poor season.
Coquelin only played because of Arteta's injuries, and we had to sit Cazorla next to him in order to have a disciplined technician in that zone comfortable at getting on the ball. We had to shift Ramsey wide and we struggled to control the midfield against organized teams. Against Monaco and Swansea in particular we could not break the opposing team's first line of pressure and impose ourselves on the game, but we were still set up to play our fluid possession style, so we eventually got hammered on the break.
It is extremely hard to beat a creative, possession-based team when they have good footballers all over the pitch who can contribute to keeping and advancing the ball. It is very easy to beat a creative, possession-based team when they have players who are not comfortable in possession, or cave in under pressure, or who don't have a big passing range, and so on, because when they lose the ball they don't have good defensive structure (and it's structure that matters, not the presence of a one-man counterattack-stopping wrecking ball in defensive midfield). We have the money now, so it's time to get complete footballers again.
And wow I just saw the Gundogan news too... gonna be hard to find the right midfielder for us.