Rodgers has enjoyed working with the veteran striker.
He told Sky Sports: "Before I came in, I was watching him from afar and seeing him maintain that real quality that he has as a goalscorer and I was really looking forward to working with him when I arrived. I was seeing the quality in the games, but it was going to be interesting to see how he was on a day-to-day basis.
"But he is right up there with the elite strikers in world football, how he threatens the line and his explosive speed over a short distance is absolutely phenomenal. He is very focused, he is in his early 30s now but he's still as quick as ever.
"He has an appetite for the game and he's got that old school mentality where he wants to fight, he wants to run and his whole attitude to the game has been absolutely brilliant since I came in. He's a natural goalscorer, if you get the service to him, he will finish."