Carles Puyol has had a terrific career with Barcelona, and it's not over yet, but the Catalan side are said to be actively looking to strengthen the centre-back position.
Partly perhaps because of Puyol's problems with fitness this season and partly because of his advancing age, Barcelona will want someone to come into the team who already has the experience and ability to fit in with some of the best players on the continent.
Here are the five defenders most likely to be targeted by Barcelona this summer.
First up we've got Kompany himself.
The Man City defender has suffered with injury this term but at his best is both a terrific organiser and a magnificent technical player.
Strong, competent in the air and good in possession, Kompany has plenty to offer Barcelona on and off the ball. As City's captain and with the club in no particular need for financial gain, Barça would certainly have to pay a top fee for the Belgian.
If he regains fitness, though, he would certainly be a top acquisition for Barcelona.
Chelsea's Brazilian centre-back David Luiz has some similar traits to current Barcelona defender Gerard Pique, which perhaps makes him less of a good fit to partner with the Spaniard.
However, Luiz's ability on the ball and proficiency to operate in a deep midfield role, as well as in defence, could make him an attractive proposition for Barcelona.
David Luiz would certainly be an expensive signing as he is on a long-term contract with Chelsea and is no doubt a big part of their plans going forward, but if the Blues fail to secure Champions League football for the coming season then he could be persuaded to move his career along.
Daniel Agger would provide an interesting foil for Pique.
Being left-footed and strong in the tackle, Agger offers the resilience and toughness which can replace Puyol's offering to the team, but he is also excellent on the ball and is very adept at moving into midfield with the ball at his feet.
Agger was said to be interesting a number of teams last summer before signing a new contract with Liverpool, but with manager Brendan Rodgers looking to continue his rebuilding programme, a big offer might tempt the Reds into selling.
Borussia Dortmund centre-back Mats Hummels has developed into one of Europe's best defenders, and he brings a magnificent combination of strength, power and technique.
Arguably he is the best all-around option for Barcelona—or any other team looking for a top defender—this summer.
He would also be likely the most expensive option.
Hummels is proven international class and would be a terrific signing for Barcelona, playing with Pique, Puyol or in the middle of both of them.
Slightly left-field, if Barcelona wanted to go for a more experienced player who had a history of being a winner, a leader and the ability of playing for one of the biggest teams in Europe, Nemanja Vidic would be an ideal signing.
Manchester United would be loathe to lose him, though the (re-?)emergence of Jonny Evans and the injuries sustained by Vidic over the course of this season might be enough to persuade both parties that a change would be in order.
Vidic is an older player, true, but Barcelona have need to replace one of the most experienced players in their entire squad, so bringing in someone with an almost equal history in the game might be a better option for them this summer.