Sigurdsson was signed from IFK Gothenburg in Sweden following Sunday's 2-0 home win over Aalborg in the final match of winger Jesper Gronkjaer's professional career.
Gronkjaer, who announced his intention to retire on Thursday, marked the occasion with a stunning goal, curling a right-footed shot into the top corner from the edge of the penalty area.
Most of the changes will occur im defence with a complete back four set to leave, including Sweden's international left back Oscar Wendt and centre back Mikael Antonsson.
Most significantly of all, Stale Solbakken, the most successful manager in the club's history, is also leaving.
After delivering a fifth league title since joining the club in 2006, he was meant to take over Norway's national team but the Norwegian FA has released him so that he can instead take the helm at Cologne in the German Bundesliga.
Solbakken's replacement will be Swede Roland Nilsson, who will make the short trip across the Oresund from his previous post at Malmo FF, where he won the Swedish championship (Allsvenskan) in 2010.
