The time Jurgen Klopp lost his temper at Ilkay Gundogan

You don't become one of the best managers in the world without a fiery temper, and Jurgen Klopp is no exception to that.

The Liverpool boss projects himself as one of the nicest managers in football (sometimes), and there is some truth behind his affable public persona. But those who have worked with him know it only extends so far.

When the German does lose the rag, though, it is usually merited. And that's something that Ilkay Gundogan knows as well as anyone. Speaking in his Players' Tribune piece, Gundogan has opened up on working with Klopp at Borussia Dortmund, and the time he inspired his rage by failing to report an injury.

Gundogan said: "As a footballer, any tiny error can put you in trouble. I know, because I once managed to make Jürgen Klopp angry. Like, really angry. 

"It was in my second season at Dortmund. We were trailing in the Bundesliga, but we had a shot at the Champions League. The staff had this rule that if you felt bad before a training session, you had to report it to the team doctor. That way we would avoid injuries, and Jürgen would know that you might not be able to train. 

"So one morning I woke up and felt my hamstring a bit. Did I have a muscle problem, or was I just tired? I couldn’t tell. I probably should have texted the doctor. 

"I probably should have texted the doctor, but I thought 'it’s probably gonna be alright'.

"Like always, I came to the training ground an hour before the session started. And just to be sure, I asked the doctor to take a look at my hamstring. He said: 'the muscle feels a bit tight. Why didn’t you text us?'

"I said: 'Don’t worry, I can train. It’s not a problem.'

"He said: 'I have to let the boss know. We can’t take any risks.' I waited a few minutes, and then Jürgen came in. He was not happy."

Gundogan says he knew he was fighting a losing battle, and it didn't take long before things escalated.

"I was trying to find a way out of it, even though I knew I was wrong," he went on. "Jürgen kept saying that we couldn’t take any risks. I kept saying that I could train. 

"And then he snapped. You know when he gets these intense eyes and grits his teeth? He gave me that look and shouted 'DO WHATEVER THE F*** YOU WANT TO DO!' then he slammed the door behind him."

The tension between the pair didn't last long before it was resolved with a hug on the training pitch, though. Klopp explained he was only angry because he didn't want him to get hurt, and Gundogan took an important lesson from the situation.

"I was shocked. We had had this fight, and now he was talking to me the way a father might talk to his son," Gundogan said. "That showed me what kind of person he is: very emotional, of course, but also very open and honest. 

Jürgen taught me a lesson that day: Always try to be honest. Both with others and yourself."