Building memorable teams at both Liverpool and BVB, the German has managed several star players through his coaching career. However, he believes the Polish striker is the best player he has worked with.
Asked about the best player he had worked with as a manager, Klopp did not hesitate in his answer.
"Robert Lewandowski. It actually won't be fair to say that about any other player except Lewy," he explained.
"What he has made out of his potential, how he pushed himself to become the player he is today, that's extraordinary."
Not just Lewandowski's innate ability in front of goal makes him such a fine player, but also his work ethic and determination.
"Lewy took every step he needed to take to be that goal machine. Every one," he added.
"He has immersed himself in the game, he just knows in every situation what he has to do, where he has to go. Lewy is an absolute machine.”
Lewandowski scored 103 goals in his 178 Dortmund appearances before he left for Bayern Munich in 2014 on a free transfer.