The Danish defender had been left out by Liverpool manager Brendan Rodgers for the five previous Premier League matches before the 4-0 win over Fulham at Anfield.
The 28-year-old is contracted to the club until 2016, and his absence from the side had led to stories he was unhappy with his situation.
"I have been waiting for this chance and, as I have said before, you have to take it when you get it," Agger told TV3+.
"I feel I have got the right to play, and of course I would have liked it to have come earlier. But in the end it is the coach who decides."
Liverpool ruthlessly dispatched Fulham, going into half-time three goals up, and Agger said keeping concentration in such a dominant team performance was his biggest test.
He added: "We didn't feel threatened, therefore it was just a matter of keeping our concentration and staying focused on what happens and not watch too much football.
"But we are happy that we had a clean sheet and scored some goals."