Agger says Rodgers has introduced a new fitness approach since taking charge last summer.
"Brendan Rodgers is undoubtedly why I have played all the matches without injuries this year, and I cannot be anything but pleased," Agger told BT.
"What the new coaching team have come in with is a form of exercise where they take into account the individual, and it is something I have needed.
"I have seen my training volume scaled down, and then I have a recovery period which is increased. And finally I have the chance to do some more specific exercises to strengthen my problem areas, all of which have helped me."