David Luiz
Chelsea appear determined to keep David Luiz out of Barcelona's hands. Reuters

After a season of dominance in Spain but disappointment in Europe, Barcelona had two objectives during the summer. The desired capture of Neymar to take some of the attacking pressure away from Lionel Messi has long since been achieved, but, with just three days remaining before the club begins their La Liga season, a center-back has yet to be secured.

The warnings had been there for some time, but last season Barcelona’s fallibility at the back became increasingly apparent. With Carles Puyol now aged 35 and restricted by injury in recent seasons, Gerard Pique not his dominant best of late and Javier Mascherano, for all his strengths in the position, not a natural central defender, new manager Gerardo Martino doubtless remains keen to add to his options before the close of the transfer window. But with less than three weeks remaining, options are now scarce. Here are three players that could yet arrive.

David Luiz (Chelsea)
After missing out on the signings of Thiago Silva and Marquinhos, it appears that another Brazilian is now Barcelona’s preferred choice. The famously big-haired former Benfica player would seem a natural fit for Barcelona with few defenders in the world as comfortable on the ball, both with his passing and drifting forward into midfield. The fact that, despite improving considerably, David Luiz can still be somewhat impetuous may mean he is not exactly the shut-down defender Barcelona need. Still, he would certainly be a welcome addition. He looks unlikely to arrive, though, with Chelsea boss Jose Mourinho insisting in recent days that the 26-year-old will not be sold this summer.

Daniel Agger (Liverpool)
Perhaps accepting that David Luiz is likely to be unattainable, Barcelona have stepped up their interest in Liverpool’s Danish center-back. A €17 million offer is already reported to have been submitted and promptly rejected. With Liverpool having turned down a bid of around €23.5 million from Manchester City last season, before the 28-year-old signed a new contract, it is likely to take a similar offer for the Premier League club to even consider a sale. Agger’s agent has unsurprisingly intimated that the player would welcome the move. Yet, with Agger seemingly not the type of character to try and force through a move, Barcelona may still find it tough to get a deal done. The left-footed former Bronby man is well-equipped with the ball at his feet and would add consistency to Barcelona’s backline.

Mamadou Sakho (Paris Saint-Germain)
With time ticking away in the transfer window, there has been speculation that Barcelona are looking at the France international, who is currently out of favor at PSG. The 23-year-old is likely to see his first-team opportunities further limited this campaign with the signing of Barcelona-target Marquinhos. Indeed, there have been rumors of Sakho’s potential departure from Paris ever since the club’s new owners started splashing the cash and putting his place in doubt. Sakho’s signing would hardly wow fans at the Camp Nou, but it is not so long ago that the left-footed center-back -- adept in possession and strong in the air -- was tipped for big things.

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