Well having 1 competent CB is better than 0. It's a start.We need a partner for Romero. No point signing a top CB to play with Sanchez or Dier.
I'd also like to think Rodon is given a chance ahead of those two. A Rodon/Romero pairing looks decent on paper.
I can't really see the second centre back we bring in being miles ahead of Rodon anyway given the kinds of funds we are talking. More likely it's a similar punt on a future prospect (looking at you Milenkovic).
We're basically pinning our hopes on Romero single-handedly saving our defence and raising the game of those around him. (With a little help from Tomiyasu hopefully).