Gerrard, 33, is nearing the end of his career and has developed into a deep-lying midfielder, making fewer forward runs.
Rodgers believes Gerrard's passing would make him a good central defender, but the Northern Irishman said the England international needed to stay fit.
"I think in terms of Steven, it (retirement) will be determined by his fitness," Rodgers said.
"He'll be 34 by the end of this season, and I look at his fitness and I look at him playing and I think that he's as fit as he's ever been. He's looking after himself.
"Of course that player that he was maybe 10 years ago, being dynamic, making those long-bursting runs forward - of course that goes out of your game.
"I think he can play as a number two centre-half later in his career.
"When you're playing against certain teams and you go one up, he can play as a right-sided centre-half, build from behind, the way he passes the ball is as good as anyone in the world."
Rodgers' Liverpool side, who are second in the English Premier League, travel to KC Stadium to face Hull on Sunday.
He expects a difficult encounter against Steve Bruce's side, but said his team were confident of collecting three points.
"They look on course to be a team in the middle of the table. So that will tell you that it's going to be a very difficult game for us," Rodgers said.
"But our confidence is high and our spirit is very strong at the moment so even though it will be tough we hope we can go and get the points."
