Sell. Our defensive vulnerability stems from his lack of effort running back. He basically leaves Fernandinho as the only midfield player with too much space to cover. Then players like Kolarov and Otamendi run out of position to cover the gaps which creates even more space in the defensive line for the opposition to run into.
Gundogan would offer so much more off the ball. His passing, vision and technique make him an excellent replacement. At 25, he's also seven years younger than Yaya.
I wouldn't be surprised if we bought another second central midfielder especially if we sell Fernando. Fernandinho has been one of the better performers this season and should hold down a holding midfield role. Hopefully, Guardiola will bring Manu Garcia into the mix even more and Delph is good as home-grown cover.
Although sometimes true, in most cases that is bollocks. Us being wide open is purely down to tactical naivety (partly due to personnel on the pitch) and also poor instructions. The fact that he is put in a 2 man midfield is purely the managers fault. We have actually looked more vulnerable when Yaya isn't on the pitch and Fernandinho and Fernando have started. Another tactic that leads to us being massively open and defenders diving in is the offside trap that Pellegrini insists on playing, it actually gets to the point where defenders don't feel they can track back without breaking this line so they dive in. I've analysed most of our games this season to check out this offside tactic and most of the time our players dive in to rush the opposition to prevent them playing an early ball through the offside line, thus being taken.
When we had Mancini we would play possession football and keep the ball until there was a way through the defence, a style of play Yaya is suited to and a style albeit adapted that we'll end up playing under Pep. Theres no reason why Yaya can't do what Xabi Alonso has done this year. Pellegrini just doesn't suit Yaya style now he's older, attacking with little structure followed by an instant counter attack leading to us giving up a lot of possession would struggle to suit any player as we've shown but in particular a player who loves to get the ball down and play football.
Ultimately the decision is with Pep and he'll be able to decide who is surplus to requirements but don't judge his decision at Barca to the decisions he's going to make. The current Yaya even with his age is better than the one who played for Barca. I'm not saying don't sign anyone, i'd still attempt to bring in Gundogan and Pogba with Fernandinho and Yaya also remaining.