Semedo's gone to Villarreal so that's a non-starter.
De Vrij might have some knee injury issues I think. Right now, I think we should just go with young and hopefully hungry than older and proven (in the Premier League). It's risky, but I kinda' hate having to keep buying someone who goes to Southampton to triple or quadruple his price before we wake up and put money in. The key is in not sinking crazy money in when they're unproven (e.g. Markovic); we did it right with Coutinho (what a fucking steal that was) and arguably with Can. So we actually can do that - we just don't do it enough.
So right now, I think we could perhaps take a chunk of the money saved from the Van Dijk deal and spend it on a younger, seemingly rising CB who has had a couple senior seasons under his belt, e.g. Issa Diop (Toulouse), Diego Llorente (Real Madrid on loan to Malaga last season), Diego Reyes (Porto on loan to Espanyol last season), Wesley Hoedt (Lazio - though Roopy thinks he might not be ready for another couple of years), maybe Nikals Stark (Hertha Berlin, though he just extended his contract recently), etc.
Not seen any of these guys in a full game, so I don't know if they're truly any good. I just wanted to name-drop a bunch of guys so I can circle back to boast if / when one of them does actually succeed a few years from now. 😀