If we do keep all of Bremer, Gatti , Djalo and Huijsen then i think we won’t look for another top CB when we already have Danilo who can cover there too, Rugani staying or leaving probably won’t have much impact in that decision, more likely we’ll be looking for two new fullbacks in that scenario, but ultimately i also do think there will still be a sell that will push us to move for another quality CB too.
In numbers, yes, four/five players for two roles. But I can't see Gatti as a reliable starter here. We don't really know where we have Djalo and Huijsen. Two big question marks and only one solid starter.
Another dimension that maybe the rest can nuance or explain... Danilo was the leader in the backline. I am not convinced he should be a starter next year and would prefer him as RB/LB and backup CB. He will also be a year older with a more intense schedule, we don't know how his body will cope with that. Anyway, what I wanted to address is that Bremer does not seem like a leader, more as someone that perform better when he can adapt to circumstances and others. That's why I thought Calafiori could have been a good signing because he seems like someone who will lead the defense. My question is, will Bremer lead our backline or do we need to sign someone to do so?
Sidenote: Gatti could probably take lead but we'd end up with a lot of additional mistakes from him. Leading costs energy and when his head is somewhere else or is tired, his performance costs us goals each time. Although perhaps he wasn't a CB-mezzela he wouldn't get that tired to begin with.