2009-10: Drafted by Rouyn-Noranda in the second round of the 2008 QMJHL Draft while playing for College Notre-Dame in Quebec midget AAA, Mallet opened the season with the Huskies after playing in ten games the previous year. Mallet skated in 39 games for Rouyn-Nouranda before being part of a multi-player trade which sent him to the Rimouski Oceanic. In 65 games between the two teams he scored 9 goals with 10 assists and was minus-23 with 85 penalty minutes. Rimouski finished second in the Eastern Division and reached the second round of the playoffs. In 12 playoff games Mallet scored 2 goals and was minus-five with 6 penalty minutes.
2010-11: Mallet skated in 60 of 68 games in his first full season with Rimouski. He was second on the team with 86 penalty minutes and was minus-one with 10 goals and 9 assists. Rimouski reached the QMJHL playoffs after finishing fifth in the East Division. In the five game series with Gatineau, Mallet had 2 assists and was minus-one with 7 penalty minutes.
2011-12: Mallet had a breakout year offensively as a 19-year-old in his second season with Rimouski. Mallet led the Oceanic in both goals and penalty minutes and his 81 points were second to teammate Alex Belzile (92). He skated in all 68 regular season games, scoring 34 goals with 47 assists and was plus-23. His 132 penalty minutes were tenth most in the QMJHL. Rimouski, after finishing fourth in the East Division, had an impressive playoff run – reaching the league finals against powerful Saint John. Mallet shared the playoff scoring lead for Rimouski with Belzile, scoring 10 goals with 15 assists, and was plus-11 with 22 penalty minutes. In his third year of eligibility, he was not among the 210 North American skaters listed in Central Scouting's final rankings prior to the 2012 NHL Draft when he was selected by Vancouver in the second round (57th overall) .
Passed over two years in a row for the draft, Mallet never gave up and was rewarded with a second round selection by the Canucks. The same perseverance makes an appearance on the ice, where his no-quit attitude and hard-nosed play has drawn rave reviews from everyone but his on-ice competition. Furthermore, he made the most of a larger role last season and showcased some offensive abilities previously unseen. A hardhat and lunch pail type of player who leaves it all on the ice, his compete level and dedication alone could take him far.