[4] Guterstam was the joint top scorer of the 2006 Superettan season with 17 goals, alongside Falkenbergs FF's Stefan Rodevåg.
[5] He was also instrumental in taking Brommapojkarna to Allsvenskan, the highest division in Swedish football, scoring two goals in the qualifiers against BK Häcken in November 2006.
Shortly after his return he signed a half-year loan contract, with an option of a permanent transfer, with Swedish club Hammarby IF.
[8] On 25 December 2010, Guterstam left IF Brommapojkarna after 8 years at the club and signed a two-year contract with IK Frej, who had just been promoted to Division 1 Norra.
[14] In the beginning of his professional football career, Guterstam also attended medical school at Karolinska Institutet in order to become a physician.