When Lukaku leaves and by the looks of it Barkley, added to the ageing centre backs in Jags and Williams, plus the massive need for a class keeper, you are talking a complete refurbishment of the whole spine of this side, apart from the central midfield area where we seem well covered with Schneids, Gana, Davies and possibly Besic if he returns well.
However, we also will need to be adding some flair and attacking players to, as I think most of us have realised now that Geri aint coming back and Mirallas is basically done for. Add that to the obviously departing Niasse, Kone and Valenica and we are basically left with no strikers!
I seriously believe we could be looking at around 7-8 incoming this summer, with most of them needing to be ready for the first team immediately.
Must have's are a new keeper, a centre back, at least 2 strikers, a couple of wide players and somebody creative in the middle depending on the formation RK will go with in big games.