Exactly! We're clearly getting rid of Kaboul (and likely Chiriches) this summer. We don't know the extent of Walker's injury yet, so even if Yedlin is ready to be a back-up in the right-back position, it makes a great deal of sense to bring in someone who can challenge Walker.
Consequently we have brought in a new CB and RB. And the transfer window has not even officially opened yet.
If people don't think a new CB and RB were a priority, then clearly they think it's fine to get rid of Chiriches and Kaboul (leaving Vertonghen, Dier and Fazio as our only senior CBs) without any replacement, while also expecting Dier to once again deputise in the RB position if Walker's injured. Madness. We can only thank our lucky stars the club doesn't share that view.
We clearly have several priorities this summer. It just so happens that our first two acquisitions are in defence (for an extremely good reason... the deal for Wimmer was clearly done several months ago; and Trippier's low release clause meant we needed to get in there before someone else snapped him up). That doesn't mean we're going to ignore the rest of the team for the entire summer. To repeat... the window hasn't even opened yet.