2009-10: Mitchell Heard opened the season with the OHL’s Plymouth Whalers, making the club as a free agent, before being re-assigned to the Junior A Bowmanville Eagles in November. In 16 games with the Whalers he scored 2 goals with 1 assist and was an even plus/minus with 4 penalty minutes. He did not appear in any playoff games for Plymouth, which finished second in the West Division and reached the second round. In 22 games for Bowmanville he scored 17 goals with 13 assists . The Eagles reached the CCHL playoff finals against Newmarket after finishing first in the East Division. Heard and Michael Markovic shared the team lead in playoff points; each scoring 6 goals with 13 assists in 22 games.
2010-11: Heard skated in 66 games in his first full OHL season with Plymouth. He scored 19 goals with 29 assists and was plus-four with 67 penalty minutes. Plymouth finished third in the West Division and reached the second round of the playoffs. Heard scored 1 goal with 2 assists and was plus-one with 10 penalty minutes in 11 playoff games. He was eligible for the NHL Draft for the second time but was not among the North American skaters listed in Central Scouting’s final rankings and was not selected.
2011-12: Heard was a point-per-game scorer while finishing second in penalty minutes for Plymouth as the Whalers finished first in the West Division. In 57 games he scored 29 goals with 28 assists and was plus-six with 111 penalty minutes (trailing only Capitals’ prospect Tom Wilson (141)). After finishing two points behind OHL champion London in the regular season, Plymouth reached the second round of the playoffs – falling to Kitchener in seven games. In 13 playoff games Heard scored 4 goals with 7 assists and was an even plus/minus with 26 penalty minutes. Not listed in Central Scouting’s final rankings prior to the 2012 NHL Draft, he was selected by Colorado in the second round (41st overall).
2012-13: Heard made his pro debut as a 20-year-old, opening the season with Colorado AHL affiliate Lake Erie and playing 23 games before being returned to juniors in January. He scored 1 goal with 3 assists for the Monsters and was -5 with 72 penalty minutes. After re-joining Plymouth as an over-age player, he scored 17 goals with 19 assists and was +14 with 34 penalty minutes in 32 games. The Whalers finished first in the OHL’s West Division and reached the Western Conference finals. Heard scored 8 goals with 5 assists in 14 playoff games and was +8 with 37 penalty minutes.
2013-14: Heard skated in 63 of 76 games for Colorado AHL affiliate Lake Erie in his first full pro season and was one of three Monsters players with over 150 penalty minutes. He had 167 penalty minutes while finishing plus-1 with 4 goals and 8 assists. Lake Erie missed the AHL playoffs; finishing fourth in the North Division.
Heard has been playing with a chip on his shoulder most of his career to good effect. He has some offensive ability but for the most part has relied on his banging style and high energy game; epitomizing the idea of "hard to play against". Played mostly an energy role in his first season of pro hockey and is willing to come to the aid of a teammate or drop the gloves to change the momentum in a game.
Heard attended training camp with the Avalanche before being returned to AHL affiliate Lake Erie to start the 2014-15 season. Subsequently sent to the ECHL Fort Worth in October, he spent a month with the Komets before returning to the Monsters. Heard is a physical player who is willing to stand up for teammates. He may not light up the scoreboard frequently but he is a player for whom opposing players are aware of his whereabouts when he is in their zone.