The designated player was acquired in a trade with the Vancouver Whitecaps on July 20 after Danny Koevermans was lost for the season with a knee injury.
But Hassli was not able to fill in for the prolific Dutch striker as expected as injuries limited the Frenchman to seven league games. Hassli scored three times over that span.
Hassli said he would have no problem working with Koevermans when he returns to active duty.
Hassli said he enjoys playing for head coach Paul Mariner and feels the former England international is the right man to turn around a team that finished 5-21-8 in 2012.
The club said Hassli, who made US$790,000 this season, will be a designated player again in 2013.