Vancouver (1-0-0) also got tallies from Terry Dunfield and Atiba Harris in its initial game. Vancouver joined the league this season along with the Portland Timbers.
The Whitecaps' first-ever goal came when Hassli scored in the 15th minute on a shot from inside the penalty area that sailed inside the left post.
Toronto (0-1-0) benefited from goals by Dwayne De Rosario and Maicon Santos but lost the first contest in MLS history between two Canadian teams.
Swim Week Miami Beach 2014 [PHOTOS]