He has since won three more league crowns and even scored the winning goal in the 2014 World Cup final, and he remains thankful to the coach who helped get his career started, even though he found him scary at times.
"[Klopp] was my first manager, and he was the one who believed in me and gave me the chance to debut at 17 years old. It’s funny to see him now with Liverpool, because he’s such a natural guy in front of the media," Gotze wrote in The Players' Tribune.
"He’s so authentic and he says whatever he wants. But I think most people just see the version of him standing on the touchline. There’s a very serious side as well. When I was 17 or 18, and not giving 100% in training, he would be so intimidating. He used to come running over and get right up in my face and start shouting at me.
"I can’t really translate from German perfectly, but you know how he talks, with his teeth grinding: 'You have to have more passion! You have to give everything! F*ck! Come on!'
"Then after training, he would be completely calm again, and he’d take you aside and say: 'Mario, how are you? Let’s talk about life. What’s happening?'"
But the Germany international also remembers the funny side of Klopp, which made an impression on the teenager.
"He knew how to handle me. He was an outstanding coach, but his personality was the most important thing for me as a young player. I have never met a manager in football who was so naturally funny," Gotze, now 26, added.
"I will never forget the time I ran into him in Dusseldorf during the summer. He was going to see the specialist there to have his hair transplant done.
"This became big news in Germany, but he was so funny about it. He was smiling, telling me all about it — how cool it was going to look and everything.
"And then as he was leaving, he just gave me a wink and he said: 'Mario, don’t worry, I will save the phone number.' I said: 'What do you mean?'
"He said: 'The doctor’s number. I’ll save it for you. In a few years, you might need it.'
"Then he laughed and walked off. Most people would be embarrassed or not say anything, but he didn’t care at all. He was such a funny and positive influence on everyone around him. I have to thank him, because he gave me my start, and we achieved some great things together at Dortmund in those years."
Pep Guardiola was in charge of Bayern during Gotze's spell in Bavaria, where he won the Bundesliga three times.
Although he struggled to keep a place in the first-team before returning to Dortmund in 2016, Gotze says he learned a lot from the current Manchester City boss.
"It is hard for me to say that going to Bayern was a mistake, because I did learn an incredible amount about football from Pep," he added.
"He could talk to you about tactics literally for hours, and I learned to see the game from a new perspective. The level of training was the most intense and meticulous that I’ve ever experienced.
"It was special to experience him as a coach and as a person, just as it was with Klopp. So I’m conflicted when I think about that time. It was extremely difficult leaving Dortmund, but if I don’t make that change, if I don’t go to Bayern, does the World Cup happen in the same way?"