"He has been class," Johnson told the club's official website. "When he first burst onto the scene, everyone could see how good he could be.
"I know he had a couple of months where he wasn't in the team as much as he would have liked, but I think he has bounced back better for that. At the moment, he's probably one of the first names on the teamsheet."
Liverpool currently have a two-point lead over Chelsea at the top of the Premier League table, with six games left to play.