The Danish centre-half forced himself to get up for the Premier League clash after his defensive partner Martin Skrtel pulled out with illness and he now admits he is in doubt for the weekend's meeting with Wigan Athletic.
"I should not have played on Sunday but Skrtel became ill and there was not much I could do. I was thrown into it," Agger told TV2 after withdrawing from the Denmark squad to play Turkey on Wednesday.
"I have a pulled groin. It was something that should have kept me out on Sunday but it did not. I played the game. It takes hopefully only a few days [to recover].
"The reason why I have cancelled for Wednesday [against Turkey] is that it is a bit early to play three days after I played 90 minutes with a groin problem."