Hellberg’s chance came at a club called Kimstad in the seventh tier of Swedish football.
He jokes he was the 12th choice and was put in a charge of a side including some of his best friends.
But proving himself is something that Hellberg has subsequently done consistently during 15 years in the dugout.
Working his way up the ranks, dispelling myths about his lack of a successful playing career, he won promotions down the divisions before landing a job in the Allsvenskan, Sweden’s top flight, in 2021 with IFK Varnamo.
Not only did he keep the newly-promoted club up with one of the league’s lowest budgets, he then took them to fifth place the following season.
That brought him to the attention of Stockholm-based Hammarby, with a bigger budget and more pressure and expectation.
Two seasons delivered successive runners-up spots, playing the attractive and fluid possession game he has brought to England, bringing him wider attention, and he was on the radar for the vacant Swansea City job before Boro grabbed him.
But with his biggest achievement possibly just around the corner, what Hellberg is most proud of is how his coaching and personality have allowed him to keep progressing.
“My perspective is very important to have with me as I know where I came from, how hard I worked to be here and I have no playing career,” he said.
“Every player I’ve coached has been better than me, even at the lowest division.
“I’ve grown a lot of confidence from that. I had to be a good person and a good coach even for [Swedish fifth-tier] Kuddby players to respect me.
“That’s been a good journey for me to always come into a club to show I’m good at this – I’m not here because I was good at playing football.
“I’m here because I’m a good person, a good coach, good at building a structure, putting a game together and developing players. That gives me belief in the long way I work.”