The most disheartening thing about last nights game wasn't the result, it was that it exposed how much this squad still needs. Sanchez, Mata and Lukaku are past it/not good enough and can't play the type of football Ole is trying to implement and using Chong and Greenwood instead isn't going to get it done, they can compete for the 6th attacking spot but we need a couple in with the aforementioned 3 being sold, and of the 2 coming in 1 of them needs some craft, not just speed.
Then there's midfield, once our counter attacking threat went off Verratti and Marquinhos had too much mobility for us with Matic in there, he's still fine as a squad option vs most PL sides, but at this level we need someone more mobile and agile.
^^^ That's just attack and midfield and we are already talking 3 buys needed and that's if Fred can actually start to contribute as well otherwise that'll be another that needs replacing.
Then there's the back 4, I honestly didn't feel CB was a huge issue last night, fullback's were though, not only are we too easy to get at with Young as RB, but at the top level we can't force the opposition fullback backwards as none of our fullbacks are good enough in attack.
There's way too much to do in one transfer window so how Ole prioritizes will be key, if we are on our usual 4 players at most plan then I think sorting the forward line out by selling the 3 that are no good and getting two in is of paramount importance, as long as teams fear the attack they wont press onto the defense as easily. Then I'd get a CM that can rotate with Matic and Herrera and hopefully Fred so we have different options depending on the games, but it's no good getting these pure DM's that offer nothing on the ball, they are useless at CL level. Then I'd get a RB because while Shaw is poor in attack he's solid defensively at least and as I said we can't do everything in one window.
I know there's no CB on the list and people will hang me for it, but that's my take on the squad right now.