The Denmark international missed Monday night's 2-2 draw at Swansea with a rib injury sustained after overstretching during a gym session the day before the game.
New signing Mamadou Sakho was handed his debut in Agger's absence and Rodgers explained his medical staff will monitor the club vice captain's fitness with a view to getting him back in the squad as soon as possible.
"We'll see how he is in the next 24 hours," Rodgers said.
"It's too early to say if he'll be ready for the weekend or not. It was just unfortunate it happened the day before the game. We're hopeful he'll be fine by the weekend."
There was better news regarding Martin Kelly, who stepped up his recovery from a serious knee injury suffered a year ago by playing 90 minutes for the Under-21s in their 5-2 victory over Sunderland on Tuesday night.
"He has been excellent in training," said Rodgers. "He is very focused on his fitness and sharpness. In the game the other night he was excellent.
"I'm looking forward to having him back and thankfully it has all gone well so far."
Rodgers also updated reporters on the timescale of Philippe Coutinho's return to the side, with the Brazilian set for shoulder surgery after falling awkwardly in Monday night's game at the Liberty Stadium.
"He's only just having it today so the timescale from the medics is obviously up to six weeks," he said.
"We wouldn't anticipate any sooner than that. It's unfortunate for him because he's been in great form since he came here in January.
"Hopefully we'll get him back sooner rather than later and then he can come into the group again.
"These things happen in football. Hopefully he'll recover quickly and come back to us in good shape."
The Liverpool manager added: "It's just unfortunate that at this moment we have had a number of injuries that have all happened at the same time because the injury record we have had here has been very good - but these are things you can't plan for and it's just something we have to deal with."