In 2011, Sundgren rejoined his former team in Lit for much of the season while Alexander Lindström was recovering from surgery, helping them finish in first place in Sweden's national Elite Series tour (though coming in second in the finals). Sundgren played with the team on much the international seniors' tour for the first half of the year and again the end of the season at the European Masters. For the 2012–2013 season, Sundgren was the full-time lead for Team Eriksson when the team relocated to Karlstad, joined also by Markus Eriksson as second, as both Alexander Lindström and Henrik Leek took a step back from curling. With the newly reorganized team, Sundgren and his teammates won the Swiss Cup Basel (2012) and European Masters (2013), as well as the Winter Universiade (2013). In the 2013-14 season, Team Eriksson reached second place at the Swiss Cup Basel, Mercure Perth Masters, and Sweden's Elite Series and competed in Canada on the World Curling Tour, coming in fifth place in three events and reaching their first Grand Slam Quarterfinal at the National. Winning the Swedish Men's Curling Championships that year as well, the team was selected to represent Sweden in the 2014 World Men's Curling Championship, as Team Edin had represented Sweden in the European Curling Championships. Though the team lost to Team Norway in the final, they defeated Team Canada, skipped by Kevin Koe twice in the event.