Amidst rumours of Javier Mascherano being ready to leave the Nou Camp, and veteran Carles Puyol's patchy injury record, Barcelona are extremely light at the back.
The Catalan club are widely known to be in the market for a world-class central defender to partner Gerard Pique.
In seasons past, Barcelona managers have experimented with lots of defensive combinations - but still haven't found the right balance.
Marc Bartra doesn't appear to be ready, while playing Alex Song or Sergio Busquets at the back is a recipe for disaster.
A humbling at hands of Bayern in the Champions League last season illustrates the need for Barcelona sign a centre-back of the highest quality.
Despite making several bids in the summer, Tata Martino will be looking to strengthen in the winter transfer window.
Here are his best five options to make Barcelona Champions League winners again:
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