The Calgary Flames had selected Wotherspoon with their second round pick, 57th overall, at the 2011 National Hockey League (NHL) Entry Draft. Flames Special Assistant to the General Manager Craig Conroy described Wotherspoon as a player whose qualities often go unnoticed: "If you're a stay-at-home defenceman that can join the rush, make the good first pass, doesn't get beat one-on-one, very sound, it doesn’t stand out." Upon turning professional, Wotherspoon was assigned to Calgary's American Hockey League (AHL) affiliate, the Abbotsford Heat, for the 2013–14 season. He had nine points in his first 48 games and a plus-minus of +13 when an injury to Dennis Wideman late in the season caused the Flames to recall Wotherspoon on an emergency basis. He made his NHL debut on March 7, 2014, a 4–3 victory over the New York Islanders. He recorded his first point the following night with an assist on a Brian McGrattan goal in a contest against the Vancouver Canucks. Wotherspoon appeared in 14 games with the Flames, recording four assists, before suffering a shoulder injury that required surgery and ended his season. Wotherspoon has been recalled and sent down by the Flames multiple times during the 2015-16 season.