It seemed a shrewd move for many reasons; Agger is a fan favourite, he's been at the club longer than most remaining players, he's an international captain with Denmark, and it likely helped solidify his affinity with the club in the midst of interest from overseas.
An untimely minor injury, however, has left Agger on the bench for the last couple of matches, despite Liverpool playing with three central defenders for three games in a row.
New signings Mamadou Sakho and Kolo Toure already seem, physically and technically, perfect fits for the Reds' back line, so the obvious fight for the remaining berth appears to be between Agger and Martin Skrtel.
So with Liverpool winning their last two games with relative ease and the back three in place performing well, should Agger be restored to the side or left on the bench until misfortune in injury or form forces one of the others aside?
The arguments are certainly there for the Dane to return.
His ability to bring the ball out of defence is well-known and well-liked, and especially with three sitting deep in defence at present, an extra body rampaging forward suddenly would not be a bad thing. Indeed, there is a case—to argue in another article—for two central defenders to alternately tilt forward into midfield.
Agger can play the central role that Skrtel currently occupies, but it is more likely that he would play the left-central role, with Sakho moving into the middle.
While the Frenchman comes to terms with his fitness, the new league and his new teammates, it's probably wise to surround him with as much service on the ball and protection off the ball as possible, while playing next to the ever-erratic Jose Enrique is another consideration entirely.
Skrtel, on the other hand, had barely featured for Rodgers in 2013, making just a clutch of league appearances after the turn of the year.
Suddenly shoved back into the team because of injuries against Manchester United, he has now played five league games in a row and looked almost back to his best. Certainly there have been few signs of rustiness or incompatibility with his new teammates.
The "why fix it if it isn't broken" train of thought has merit, but that's not to say that Liverpool's defence is perfect right now or can't be improved further.
Even in a relatively routine win over Crystal Palace recently, Liverpool still conceded a lot of ground and chances on goal, and the central defender is often the one most called upon to do clearing and sweeping up work.
Sakho's emergence at Anfield means fans will certainly rest assured if he is the one asked to do such work, while elements of doubt remain over Skrtel's decision-making, his tendency to jump around the front of challenges and his heading.
That said, he made 12 clearances against Palace, won three of six headers and completed 94 per cent of his 53 passes. He also committed three fouls, while neither Toure nor Sakho made any.
Agger himself would admit he was not always at his best last season, though his form certainly picked up significantly over the second half of the campaign and into the start of this one. However, small but repetitive failures need to be eradicated from his game, such as marking from set pieces—an extra central defender helps there—and, at times, his agility in one-on-one situations.
Again, playing on the left of a three-man back line, should aid improvement and progression.
Agger is certainly a level above Skrtel in the normal course of being a Liverpool defender, but that doesn't seem to be enough for some people—Brendan Rodgers included, so far—to warrant removing Skrtel from a winning team.
With all four senior defenders on intensive international duty this week, the manager's hand might well be forced through fatigue or injury to change things anyway next time out, but if all four remain available it will be fascinating to watch the development of this four-way battle for three spots.
Defensively the system is working; in attack it's working too. Liverpool have a little bit to sort out in midfield, but with returning players might also come a return to a four-man defence.
Rodgers' decisions on formation and crucially his centre-backs might well be key on how long Liverpool can keep up their charge at the top of the Premier League.
Agger's got to surely come back in at some point; the question for Rodgers is: Does he do it now or wait until Skrtel makes what might easily be a costly mistake to change them around?
Stats via Squawka