Before his rise as Europe's goalscoring champion, Robert Lewandowski struggled to make a mark in football. But after signing with Borussia Dortmund in 2010, the Polish striker saw his game improved and he credited the big change to his former coach Jurgen Klopp.

The German, according to Lewandowski, is "a bad teacher," and it was not a bad thing then. Then a young forward, the Bayern Munich star submitted to the system of Klopp and he went through a difficult process of transformation.

The training under Klopp, however, made Lewandowski the deadly striker that he is now. He is an A-player and the Liverpool boss was partly responsible, the Polish admitted.

Lewandowski is not yet the respected marksman that he is when he first met Klopp at Dortmund. The entry to Bundesliga saw the forward struggling to adjust with the system and that continued through his second season with the German side.

"When the second season began, I was still struggling ... I also felt that Jurgen wanted something from me, but I didn't understand exactly what," The Mirror reported the Bayern star as saying.

A humbling defeat in the Champions League proved the turning point for Lewandowski so he approached his coach and the two had a defining talk. The next game turned out inspiring for the Poland international. Dortmund scored a win on the back of Lewandowski's hat trick and there was no turning back after that.

The player and coach worked for a total of four seasons at Dortmund and before moving to new sides, they collaborated to win several trophies, and the most notable of which were the two Bundesliga championships that Lewandowski has a claim on.

He continued the winning tradition starring for the Bavarians but Lewandowski made clear he owes his success to Klopp. The German played the bad teacher while leading Dortmund and the players learned to give their best because the coach encouraged and demanded it.

"He taught me so much ... He was not content to let you be a B student ... Jurgen wanted A+ students. He didn't want it for him. He wanted it for you," Lewandowski explained, and per the report by Goal.

Klopp was a bad teacher in the sense that he is the one that students easily remember, and that's because he taught lessons with a long-lasting impact. And most importantly, Klopp also played the father figure - a boss that is strict but is open, trustworthy, and easily relatable.

In 2014, Lewandowski made the move to Bayern and his rise only continued. The year 2020 turned out as the most defining for the star as the Germans achieved a treble and capped that by capturing the Champions League crown. Before the end of the year, FIFA recognized Lewandowski as the best player in Europe.