By Chris Myson & Pilar Suarez
Barcelona were already doing their homework on possible defensive signings before Carles Puyol's announcement that he will be leaving moved the issue to the top of the club's agenda.
With the veteran of almost 600 first-team matches, who turns 36 next month, making his Camp Nou departure, the club are committed to signing a high-profile centre-back and are prepared to spend big if that is required to land a player of the necessary quality.
Barca's back four has been seen as one of the squad's only weaknesses for a number of years, but the last two seasons have proven even more problematic than most for the defence.
Puyol has been on a continuing physical decline, Gerard Pique's form has slumped significantly since his peak performances after arriving from Manchester United, while Javier Mascherano, a holding midfielder by trade, was converted to central defence.
The club's preference for attacking full-backs, highlighted by current first-teamers Dani Alves and Jordi Alba, often leaves the back line exposed. Set pieces are another problematic area, with a lack of height seen as a continuing issue since Eric Abidal's departure.
Now, Barcelona are ready to act. The club's preference has always been to promote from within and, as well as signing a new star at the back, they are also prepared to put their faith in Marc Bartra.
A new contract has been announced to keep the La Masia graduate at the club until 2017 and insiders at the club are genuinely hopeful that Bartra can develop into one of the world's greatest defenders in the coming years.
Any option of selling the 23-year-old stopper has now been dismissed and coach Tata Martino is ready to give him an increasingly significant role in the first-team.
Despite being heavily linked with Napoli, Mascherano still has a future at the club, too – if Martino hangs around. He is another of the coach's favourites and is seen as an experienced, reliable figure for use in the biggest matches.
|BARCA'S TOP FOUR DEFENSIVE TARGETS
| ELIAQUIM MANGALA
|Powerful centre-back who has made his name at Porto and gained France recognition. He has European experience and is still only 23, but is also targeted by other top clubs and the price could be high as a result.|
| EDER BALANTA
|Still relatively inexperienced at the highest level, currently playing for River Plate and Colombia. The 21-year-old is well known by Martino and heavily tipped for a bright future.|
| MATEO MUSACCHIO
|The only current target who has experience of playing in Spain. Has impressed for Villarreal as they chase a Champions League spot. The 23-year-old Argentine has a price-tag of around €30 million.|
| DAVID LUIZ
|The highest-profile name in the shortlist. Approaching his peak years at 26, the Chelsea and Brazil defender's style of play could be ideal. However, there is no guarantee the Blues would sell.|
As things stand, there are four leading candidates on Barcelona's shortlist. They are Eder Balanta, David Luiz, Eliaquim Mangala and Mateo Musacchio.
Balanta is perhaps the least familiar name to many Barca fans. The 21-year-old plays for River Plate and has recently made his debut for the Colombia national team.
He was in the city playing against Tunisia in an international match held at Espanyol's stadium earlier this month and spoke at length about his dream of playing for Barca. Martino has a strong knowledge of South American football and is close friends with Jose Pekerman, Balanta's coach with Colombia.
In comparison, Chelsea and Brazil star David Luiz is undoubtedly the best-known player on the list. His style of play as a technically-gifted defender would seemingly be an ideal fit, but the fact he plays for another major European club who would likely demand a high price-tag - if they could be persuaded to sell at all - means pursuing that interest is by no means certain.
Porto star Mangala has caught the attention of clubs across Europe and was heavily pursued by Manchester City in January. He already has European experience and, at only 23, has room for further progression.
Musacchio, another 23 year old, has enjoyed an impressive season for Villarreal as they challenge for European qualification in their first season since returning to the top-flight.
Martino is a known admirer and was seen speaking to him when the Yellow Submarine faced Barca in December but, publicly at least, he has denied any talk of an upcoming transfer.
Other names have also been on the rumour mill in recent weeks, with two of the newer suggestions touted by the Spanish press being Mehdi Benatia of Roma and Real Sociedad's Inigo Martinez.
Borussia Dortmund stopper Mats Hummels was considered a top target for a spell but, while he is still a candidate, he has fallen down the list as he endures a season of poor form and concerns as to whether he is at Barcelona's level.
Vincent Kompany was also linked with the club recently but that is not seen as a likely move. The speculation is considered more fantasy football than reality, with press reports having been heightened by the two teams facing each other in the Champions League.
So there are plenty of options for Andoni Zubizarreta, Martino and those in positions of influence at Barca. Some targets are more likely to arrive than others, but what is clear is that one new face is expected to arrive at the back.
Martino has indicated he would be happy with his options after Puyol's departure if he had Bartra, Mascherano, Pique and a new signing at his disposal in the centre. At left-back he has Alba and Adriano, while at right-back there is Dani Alves and Martin Montoya.
The future of the right-back spot is least certain. Dani Alves' contract expires in 2015 and, as yet, there have been no concrete moves towards extending that and the Brazilian has been linked with various sides.
There have been negotiations with Montoya, who is out of contract this summer, and he is expected to sign a new deal until 2018, although Inter are still heavily chasing his signature and cannot be ruled out.
If one of the right-backs leave, Napoli's Juan Camilo Zuniga, who has stated he would be keen to join, is a possibility but, with Adriano also capable of covering there, that position is not as high as a new centre-back is in the priority list for now.
Barca are confident that their defensive issues will soon be a thing of the past if their transfer market goes according to plan in the summer.
A new centre-back to complement Bartra - who is set for an increased role - plus Pique and Mascherano should see the position become one of strength and depth with strong competition rather than the weak link it has been in recent times.