A native of Surrey, British Columbia, Wotherspoon was selected by the Portland Winter Hawks in the second round of the 2008 Western Hockey League (WHL) Bantam Draft. He made his WHL debut as a 15-year-old in 2008–09, appearing in four games for Portland, then played four full seasons between 2009 and 2013. In his WHL career, he has appeared in 239 games in his WHL career and scored 17 goals along with 65 assists. With the Winterhawks, he appeared in the WHL championship series in three consecutive years as Portland lost the final in 2011 and 2012 to the Kootenay Ice and Edmonton Oil Kings, respectively, before finally winning the Ed Chynoweth Cup championship in 2013 by defeating Edmonton. Wotherspoon was also named to the WHL's Western Conference second All-Star Team in 2012–13. Wotherspoon scored three points in five games at the 2013 Memorial Cup, however Portland lost the Canadian Hockey League (CHL) championship game, the Memorial Cup, to the Halifax Mooseheads, 6–4. During the season, Wotherspoon was also a member of the Canadian junior team, recording two points in six games at the 2013 World Junior Ice Hockey Championships.