Five CBs is excessive but only because you expect at least one senior DM / fullback to be able to cover if four isn't enough... and I reckon you'd probably want a half decent youngster kicking around as well.
Right now, Rodri is barely in the picture as cover because Philips is injured, and Walker is the only RB until Gomez proves he is ready, which remains an if. I don't doubt his technique, but he's clearly being asked to step up physically.
That's with one injury in midfield.
I see four potential open slots in this squad.
A winger with pace. Like: Leao.
A senior LB who won't get bullied and can play. Like: Lodi
A central player, quite possible another ball carrier as KDB is so far up and we are playing much more of the pitch at once. Like: De Jong
The fourth is a suitable RB, with some of Kyle's physical attributes, but younger or more technical.
Now, if we go on to sell Bernie, my clear opinion is we would need two of the first three to make it safe.
If we keep him, the priorities are less clear to me, but I think a utility RB stopgap / long-term Kyle replacement would solve several issues - even if some are only potential issues, it's already too close for comfort.
We should stop here, and remember we sold our experienced LB. In addition, we sold Lavia (DM/CB) to a prem club, Porro and Kabore (both RB) to sides in today's CL draw. Those are the players who - in addition to Cucurella - would make this situation safe. I'm not saying we were wrong to let them leave. I am saying tho, those decisions contribute to why we feel under pressure right now. And it's the same with incomings, Philips injury is recurrant, and Gomez is being asked to step up.
My feeling is clear, this one is on the board. Haaland changes so many things for this club. I don't think tho, that excuses them from the obligation to provide the manager with a squad of sufficient depth.