The forward has been out since he limped off in the win over West Ham in November with a knee injury.
He still went to the World Cup with England but failed to feature and returned with another knee issue which has sidelined him since.
The 26-year-old has resumed training and is in contention to face Brighton at the King Power Stadium on Saturday and Rodgers believes he will be the biggest January arrival in his squad.
“Yes. He is such a massive talent and he has improved so much in every way from seeing him when I first came here,” he said.
“He is one of the top players in the Premier League in every facet of his game. To have that missing from our team makes a big difference. It will be brilliant to have him back.
“That quality he brings to the team, we don’t have anything like it. That’s the reality. Players of that quality give confidence to other players. Everything else moves from that.
“He can create space, he can keep the ball, he can stay on it, he can create. The big area of his game that has improved is the intensity in his pressing. Getting him back in the fold brings a different dimension to us.”
Without Maddison Leicester have lost their last four top-flight games to sit 15th in a congested table, two points above the bottom three.
“If you look at the league it has fantastic coaches, fantastic clubs, so it’s very competitive. I think right the way through until the end it will be a fight for every single team,” said Rodgers.
“If you win a few games you jump a number of positions, so for us that is our idea – to in this second half of the season climb into that top half.”
Leicester are expected to strengthen for their survival fight and defender Victor Kristiansen is close to joining from FC Copenhagen as the Foxes look to sign their first permanent player in the January window since 2018.
“It’s nice. It’s not all about new players all of the time,” added Rodgers.
“Obviously in our position I have always felt with this squad that regeneration is so important – for every team.
“I have been here nearly four years, normally teams are changing after three years.
“If we can get a few in that will help energise the team. But teams out there are competitive now, they want to develop – and they can go and improve their squads.
“Clearly there are finances there and they want to improve. Our first place to look is always within for young talent, if not you look outside and most teams have done that.”