The England international missed the opening games of the Premier League campaign after suffering an injury in pre-season.
Since returning to action, the midfielder, who scored his first Liverpool goal in the Reds' 2-1 victory over West Bromwich Albion prior to the international break, has impressed the manager.
"His fitness is growing all the time," Rodgers told reporters. "I see him in training and he's showing real signs of getting back to the top of his game. He's going to be an exceptional player for us and he will get better as the season goes on."
Lallana is likely to play in Sunday afternoon's match against Queens Park Rangers at Loftus Road.