Upon helping Malmö return to the top division on the first time of asking, Söderberg was signed to a lucrative three-year entry-level contract with the St. Louis Blues on 1 June 2006.

Söderberg was to be assigned to the Blues American Hockey League affiliate, however struggling to adapt to his new country and dealing with homesickness, refused and was returned on loan to continue with Malmö in the SEL.

[4] With the injury ruling him out for the remainder of the season and unable to practice in the off-season, Söderberg was traded by the Blues to the Boston Bruins in exchange for Hannu Toivonen on 23 July 2007.

At the conclusion of his NHL deal, and with the Bruins retaining his rights, Söderberg opted to remain loyal with his hometown club in Malmö, who were also threatened bankruptcy, for a further two seasons.

[6] After 10 seasons within the Redhawks organization, with the club unable to earn promotion from the HockeyAllsvenskan, Söderberg in order to advance his career agreed to a one-year deal with Linköpings HC of the Elitserien on 1 April 2011.

Upon Linköpings exit in the post-season, with the ambition to embark on an NHL career, Söderberg settled a protracted dispute with the Swedish Ice Hockey Association.

[15][16] On 25 June 2019, with a year remaining on his contract, Söderberg was traded by the Avalanche to the Arizona Coyotes in exchange for Kevin Connauton and a 2020 third-round draft pick.

Söderberg helped the Coyotes qualify for the post-season recording a goal and an assist in nine games, before suffering a first-round series defeat to former club, the Colorado Avalanche.

Helping the Avalanche sweep the Blues, Söderberg later scored his first goal in his return to Colorado during the second round series game 3 loss to the Vegas Golden Knights on 4 June 2021.

As an impending free agent, Söderberg effectively opted to conclude his career in the NHL after nine seasons and 597 games, returning to his native Sweden and signing a two-year contract with his hometown club, the Malmö Redhawks of the SHL, on 17 June 2021.

Söderberg finally made his return to the national team after he was selected to take part in the revamped 2016 World Cup of Hockey in Toronto, Ontario at the Air Canada Centre.