Johnson has over the last 12 months been switched from the right of defence to the left, returned and then moved back again.
Rodgers feels that has hidden the influence he has had, particularly this season.
"Glen has arguably been the player of the Premier League, never mind Liverpool," said the Reds boss.
"He has been absolutely outstanding when you consider he has played a lot of the season at left-back.
"He is a world-class full-back and when you miss a player of that quality it does weaken you as a team, of course.
"I look at him and (Barcelona's) Dani Alves as the two best right-backs in world football.
"I don't know how he has been beforehand but he is absolutely fantastic.
"He has shown he is a top player and I've been very impressed with Glen: his attitude to training and the game and the fact he's had to fill in at left-back because of Jose Enrique's injury this year."