How much of a priority is signing a centre-back this summer?

Central midfield and wingbacks should be the top priority. Then striker. Then CB. Then GK
 
It'd be a low priority for me but when free agents like Rudiger are available we should be looking at them.
 
Would you say he's worth £400,000-per-week like some have suggested are his demands?
No and i think getting him is unlikely even leaving that aside. Theres a few cb's who seem likely to move this summer for not too crazy prices though. I'd keep an eye on the market, same for most other positions.
 
Would you say he's worth £400,000-per-week like some have suggested are his demands?

I think he asks 200k-250k p/w since his current one is only 100k while the other chelsea players like werner, havertz, lukaku, Saul, and etc are getting double or more than him. Well, if we let Pogba go, he can have Pogba's 290k p/w. Rudiger's signing could be potential a risk since he might not be motivated anymore to win or it could be great free signing since he's better than Maguire. And also signing Rudiger will be a great message to Maguire that you need to level up or sit on the bench and say good bye to your England National Team career.
 
Having had the keystone cops at the back thus season, Maguire my word what can you say, its undefendable, of how many mistakes he's made this season. He's going to stay, if so next manger needs another CB In, captaincy taken off him. The CL game Athletico, the front 2 pressed him only when he hangs onto the ball to long the whole opposition pressed, it made everything harder, Varane doesn't hold the ball long finds a pass quicker.
 
Goalkeeper is a bigger issue, if we actually had a commanding sweeper keeper we would look far more assured in our penalty area instead of the mass panic all the time because de gea is afraid of physical contact and to come off his line and we also wouldn't have to worry so much about Maguire's lack of mobility/pace