Kassian, 24, had 10 goals and 16 points in 42 games for the Canucks last season. In 2013-14 he set career-highs with 14 goals and 29 points in 73 games.
Taken by the Buffalo Sabres with the 13th pick of the 2009 draft, Kassian has 35 goals and 66 points in 198 games with the Sabres and Canucks.
Prust, 31, had four goals and 18 points in 82 games last season, and four points in 12 Stanley Cup Playoff games.
Introducing the new official NHL App, available for iPhone, iPad and Android smartphones and tablets. A host of new features and improved functionality are available across all platforms, including a redesigned league-wide scoreboard, expanded news coverage, searchable video highlights, individual team experiences* and more. The new NHL App on your tablet also introduces new offerings such as 60fps video, Multitasking** and Picture-in-Picture.
*Available only for smartphones
** Available only for suported iPads