On a cold, wintry Sunday morning in 2012, he rented a car to get to his first coaching course. Since then, many coaching opportunities have come and he has climbed from the lower divisions to the Allsvenskan.
After taking Västerås SK to the top league - twice - the football journey has taken Kalle Karlsson back to Stockholm.
In the capital, where he was previously responsible for Karlberg and Vasalund, he is the coach expected to lead Hammarby to long-awaited success.
The club is also the favorite, according to coaches and media.
Not sure
"I don't know if it's an advantage or a disadvantage to be tipped to be at the top. But it's fun, it shows that we've done something good at the club," he says.
"Then it's clear that I would have placed more importance on this if it had only been the coaches who tipped. Now that the media has been involved... I know that they don't have such a good grasp."
At the same time, success and Swedish Championship gold are exactly what the fans hope for.
After many years without a Swedish championship title - the only Swedish championship gold was won at home in 2001 - thousands of supporters marched from Medborgarplatsen to 3 Arena to watch the season opener against reigning champions Mjällby.
They did it with - as usual - high expectations.
Karlsson?
He treated the opener like any other match.
“Small difference”
"Everyone expects there to be a huge difference. But there is much less difference than people think. I do the same things I did before," he says, comparing the spotlight in Hammarby with his time in Västerås.
"Football grew a lot there. When we were in the Allsvenskan, there were just over 8,000 at the big matches. The office said that if it had been a better arena, they would have sold 15,000 tickets. There was a lot of interest there too."
At the same time, the 3-0 victory in the opener, in front of a packed stadium, was something special.
"It was amazing. It was definitely an electric atmosphere in there. I think it was a wonderful feeling for the players running around out there; it was for me on the sidelines too."
Kalle Karlsson, whose contract runs through 2028, doesn't know how the season will end or what the future holds.
He says that in the pursuit of the Swedish Championship gold, it's important to have the full picture and some luck. At the same time, he has not closed the door to journalism, which he left in 2021 when he became head coach of Västerås.
"You never know what will happen in the future."
Facts: Karlsson
November 23, 1981.
Occupation: Football coach.
Previous profession: Sports journalist.
Club: Hammarby, contract extends to 2028.
Previous clubs: Karlberg, Vasalund, Västerås SK.
Main achievements: Promoted Västerås from Superettan to Allsvenskan twice.
Current: Is Hammarby's new coach.
