Lewandowski has no doubts about the 18 year-old's ability and potential, though wonders whether Yamal can maintain his progress long-term.
He told The Times: "How do I manage the new generations in the Barcelona dressing room? I have to say it was a huge challenge. I came from a different generation, and I had to learn to think about how to get the best out of them.
"Before, shouting was a way to motivate. Now, if you shout too much, this generation's reaction isn't the same. Their reaction isn't to prove you wrong. No, now you have to explain things differently. You have to talk a lot. They don't like being yelled at. Now you have to focus more on the mental aspect of football."
On Yamal specifically, Lewandowski also said: "In my first training session, Lamine was 15 years old. It was the end of the season and some players were trying out for the team. Lamine was playing against an experienced left-back and did what he wanted. I've seen many good players who needed time, but Lamine didn't.
"I'd never seen that kind of talent at that age. His challenge? To still be hungry in three or more years. I doubt starting at 16 at the top level can last 20 years."