If the team doesn't get an upgrade in defense, we're f.ed, especially Chiello getting older means Bon getting more responsibility. IMO, Bon is not up to that.
Manolas doesn't strike me like someone that could carry that responsibility either - but might be wrong.
Other than Romero, that everyone says is good, I don't know who could be signed to improve the defense, or keep it at the same level. Would love if Rugani steps up his game untill the end of the season. The experience he's getting by playing with Chiello and Bon now is really gonna be a waste if we sell him.
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Now that I think of it, we would be especially screwed, considering our LBs/RBs are defensively very mehh too (Canecelo, Mds...).
Also, Bakayoko, would be great I think.