The reason Barcelona are looking to get another centre-back is the lack of depth in that position.
Barcelona are trying to sign David Luiz, but the Blues are determined to keep the Brazil international, so who can Barcelona bring instead of him?
Daniel Agger | Liverpool
The Liverpool centre-back has been confirmed as Steven Gerrard's vice-captain earlier this week. Barcelona have been tracking the big Danish defender from last season, and might be ready to seal the deal this summer.
Liverpool, of course, won't let him go very easy - they want him to stay in order to get back into the Champions League, but I think that with the right amount of money he would land at the Nou Camp.
Estimated Price: £15-20m. Low money for a young, impressive leader.
Eliaquim Mangala | Porto
The young French centre-back is one of the brightest players in the world.
Chelsea were following him until Porto set a high transfer fee for him. The 22-year-old, who has already made one appearance for Les Blues, joined Porto in 2011 from Standard Liege and made 30 appearances and even scored four goals.
The Frenchman has been a part of seven major titles in both Portugal and Belgium.
Estimated Price: €45m. His release clause at Porto.
Toby Alderweireld | Ajax
Ajax are known for the young footballers they have produced over the years, Toby Alderweireld is part of the Belgium golden era and is an established player in the Belgium defence with Vincent Kompany, Thomas Vermaelen and more.
Ajax's 24-year-old defender will very much welcome a move out from the Amsterdam Arena - and more than five clubs have expressed their interest in the player.
Estimated Price: £10-15m. A decent spending for a centre-back who will be a back-up.
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