Barcelona have lodged a formal bid for Liverpool defender Daniel Agger, according to the Mail Online. It is believed the Spanish champions have offered £17m for the Danish international.

This is not the first time Barcelona have been linked to the Dane. Reports from Spanish publication Sport, early in June, identified Agger as a possible target; at the time it was believed the entire Barcelona first team would be revamped following a miserable performance in the 7-0 Champions League aggregate defeat to Bayern Munich.

Daniel Agger

In addition, it is believed Barcelona are also shopping for a new centre-back to act as long-term replacement for 35-year-old club captain Carlos Puyol. The veteran Spain international is the undisputed heart and soul of new manager Gerardo Martino's team but his age and increasingly severe injury problems highlight an obvious need for reinforcements.

Agger is contracted to Liverpool till 2016 and has previously expressed his support for the club. However, it remains to be seen if the temptation of playing for a club like Barcelona will rise above that commitment.

In either case, the bid only increases pressure on Brendan Rodgers, who is still defending the club from Uruguay striker Luis Suarez's attempt at a forced transfer to rivals Arsenal.

And the move for Agger comes almost immediately after an offer for Chelsea defender David Luiz. An earlier Mail report said Nou Camp chiefs made a £34.5m bid for the Brazilian, who previously interested the Catalans' fierce rivals, Real Madrid.

Reports say the offer for Luiz was promptly rejected and Chelsea have made it clear the 26-year-old is not available for transfer. The former Benfica man enjoyed a strong close to the 2012/13 season under interim boss Rafael Benitez, moving from a defensive role to a holding midfield position with impressive results.

David Luiz

Chelsea boss José Mourinho has confirmed he sees Luiz as an important member of the first team at Stamford Bridge but has also admitted concern at certain aspects of his game. The former Santiago Bernabeu boss is keen to work with Luiz though and improve his overall performance.

"I have known of David Luiz from the very beginning so I know him very, very well. I see him as a centre-back because he has an important quality for a footballer - he can build from the back. He is very comfortable and confident with using the ball from the back - he does not play direct," the Portuguese explained.

"And he can improve, especially defensively. He can be much more effective, much more solid. But the potential he has is amazing, incredible," he concluded.

Martino, who replaced Tito Vilanova only a short while ago, is aware he needs to strengthen his central defensive options, with only Gerard Pique and Puyol as specialist first-choice centre-backs. Another Brazilian international - Thiago Silva of Ligue 1 champions Paris St Germain (PSG) - was also linked to the Spanish club but Parc des Princes officials have ruled out a sale.

Puyol's Second Wind

Meanwhile, it may transpire Barcelona do not recruit a new centre-back this season. A report in Marca claims Martino and his assistants have been impressed by Puyol's recovery rate.

The Spaniard is presently recovering from a knee operation but is expected to be fully fit inside the next month. The report also claims Martino is happy to continue with defensive midfielder Javier Mascherano as a makeshift centre-back, while also relying on La Masia youngster Marc Batra to fill in when needed.