2010-11: Mason McDonald played goal for the Halifax ACCEL Hawks major bantam team that advanced to the Nova Scotia provincial tournament.
2011-12: McDonald played for the Nova Scotia midget AAA champion Halifax Titans. He had a 2.01 goals against and .916 save percentage in 20 regular season games and had a 2.03 goals against and .932 save percentage in six playoff games. Halifax finished third in the Atlantic Regional tournament as Moncton earned the right to compete in the Telus Cup. McDonald was selected by Acadie-Bathurst in the second round (20th overall) of the 2012 QMJHL Entry Draft.
2012-13: McDonald appeared in 26 QMJHL games with Acadie-Bathurst as a 16-year-old and played for Canada Atlantic in the 2013 U17 World Hockey Challenge. He was 6-8-3 with 1 shutout and had a 4.72 goals against and .885 save percentage in QMJHL play. The Titan finished fourth in the Maritimes Division and lost to Blainville-Boisbriand in a five-game first round playoff series. McDonald played one period as a backup to Jacob Brennan in the playoffs; stopping 12 of 13 shots. In four games at the WHC he finished with a 5.34 goals against and .870 save percentage for Canada Atlantic.
2013-14: McDonald played for Canada’s U18 team in the Ivan Hlinka Memorial and World Junior Championship tournaments. He began his second QMJHL season with Acadie-Bathurst before being acquired by Charlottetown in exchange for three draft picks at the end of December. In 29 regular season games between the two teams he was 8-15-3 with a 3.44 goals against and .900 save percentage. Charlottetown reached the playoffs despite winning 21 of 68 regular season games and was swept by Halifax in a first round series. McDonald started all four games and had a 6.58 goals against and .860 save percentage. He did not appear in any games for Canada’s gold medal squad as a backup to Julio Billia at the Ivan Hlinka tournament but was 4-2 with a 1.94 goals against and .930 save percentage in six games for the bronze medal squad at the WJC. McDonald was selected to play for Team Orr in the 2014 CHL/NHL Top Prospects Game. He was ranked second amongst North American goalies in the Central Scouting final rankings and was selected by Calgary in the second round (34th overall) in the 2014 NHL Draft.
2014-15: McDonald played a career-high 56 games during the regular season for Charlottetown in his third QMJHL season. He was 28-22-4 with 1 shutout and had a 3.06 goals against and .906 save percentage. The Islanders finished second in the Maritimes Division and reached the second round in the playoffs. A knee injury hampered McDonald in the playoffs, limiting him to 3 of 10 games for Charlottetown. He was 1-1 with a 3.98 goals against and .879 save percentage. He signed a three-year entry-level contract with Calgary in July 2015.
McDonald is a battler between the pipes who never gives up on the puck and makes the most of his size and athleticism. Though he has frequently found himself peppered with shots, the netminder is unflappable under pressure. Pairing a big frame with great mobility in the crease gives McDonald the foundation to be a special prospect.
McDonald attended Hockey Canada's U20 evaluation camp over the summer and will be in his second training camp with the Flames before likely returning to Charlottetown for his fourth QMJHL season in 2015-16. He is among the leading candidates to play for Canada at the 2016 World Juniors. McDonald made great strides in his first season as a starter at the major junior level last year. With talented prospects Joni Ortio and Jon Gillies also in the system the Flames can afford to be patient with McDonald. His physical attributes and technical skills suggest he can be an elite netminder one day.