Daniel Agger
Agger's future at Anfield in doubt.GettyImages

Daniel Agger will quickly become "frustrated and irritated" should he remain a marginalised figure at Liverpool, Denmark coach Morten Olsen believes.

The 29-year-old Agger, who has been the subject of interest from Barcelona during the past two summer transfer windows, started the campaign as Brendan Rodgers' first choice centre half but slipped down the pecking order amid of a season of inconsistency and injury.

The Dane started just 16 Premier League games during the 2013/14 season as Rodgers opted for the centre half pairing of Mamadou Sakho and Martin Skrtel.

Agger recently aired his frustrations over his peripheral role at Anfield and admitted his future at the club depends on the decision of his manager. But his national team coach has advised the Liverpool vice-captain to think carefully about his future to ensure his own happiness.

"You may ask Daniel about it," Olsen told Bold. "He can best gauge how it looks now and, more important, next season.

"But of course he should be playing. Otherwise, I believe we will have a frustrated and irritated captain. I hope he will make the right choice."

With Barcelona's already limited defensive options to take another hit this summer in the retirement of Carlos Puyol and doubts over Javier Mascherano's future, the club could be expected to return to Liverpool again this summer with an offer for Agger.

The Dane's former manager Rafa Benitez has also been credited with interest in bringing him to Napoli and Agger's recent comment suggest he will be willing to listen to offers in the coming months.

"No, I'm no one's third choice. It definitely wasn't great [not starting regularly]. But I don't make the decisions. I can't go and put myself on the team sheet. I think it is because the manager doesn't think that I'm good enough. I don't know [if I'll be with Liverpool next season]. That's up to the manager," Sky Sports quoted Agger as saying.