Horvat, 19, appeared in five games with the Canucks during the 2014 NHL Pre-Season games registering one goal (1-0-1). Last season he appeared in 54 games for the OHL London Knights collecting a career-high 74 points (30-44-74) and 36 penalty minutes.
The 6'1", 216-pound centre was originally selected by Vancouver ninth overall in the 2013 NHL Entry Draft.
Griffith has skated in three games for Boston during the 2014-15 season. He tallied 20 goals and 30 assists in 69 games last year with Providence.
Spooner has skated in five games with Boston so far this season, bringing him to 32 career NHL games. During the 2013-14 season Spooner skated in 23 games for Boston notching 11 assists and skated in 49 games with Providence scoring 11 goals and earning 35 assists.