Sami Hyypia has not trained this week because of illness and Benitez says he be prepared to partner Agger alongside Jamie Carragher against Pompey.
"It's a possibility. I need to check because Sami Hyypia was sick for one or two days. The new boys are not 100 per cent physically fit, but they will have enough physical condition to play in this game," said the Liverpool manager.
"The question will be to see how we can use different players and still have a strong team."