I think Joe Gomez is very much the deputy defender. He hasn't played well enough to warrant being the first choice CB for us, and to be fair, in more recent performances he hasn't looked nearly good enough in my opinion. He is versatile in that can cover both CB roles, and also the RB role, has been at the club for a while and understands our systems. I doubt he'd be on massive wages either. So overall, I think he's a player that I would keep around for now, but sooner or later we are going to find a younger, and better understudy.
I genuinely don't think our problems are at CB. We have 4 'good enough' CBs. Admittedly, they've all struggled with form, consistency and injuries this season. I do think that if collectively the team does better with our pressing, shape and defensive capabilities, then our CBs will look better too. I'm sure that when it comes time to renew contracts, then we will be thinking carefully about whether there are alternatives to VVD and Matip out there.