2009-10: Drafted by the Tri-City Americans in the fourth round (80th overall) of the 2009 WHL Bantam Draft, Driedger skated for the Winnipeg Monarchs in the Winnipeg City midget AAA league and was selected to Team Manitoba in the 2009 U16 Western Canada Challenge Cup. In twelve games for the Monarchs he had a 1.75 goals against average. Driedger spent some time with Tri-City during the year but did not see any game action.
2010-11: Driedger appeared in 22 games for Tri-City in his first WHL season and played for Canada West in the 2011 U17 World Hockey Challenge. Backing up Americans' starter Drew Owsley, Driedger saw the bulk of the action in February, when he played in eleven games and was 4-5 with one of the losses coming in a shootout. For the season, he was 6-7 with a 3.50 goals against and .811 save percentage. Tri-City finished third in the U.S. Division and reached the second round of the playoffs but Driedger did not play in any playoff games. He was 1-3 with a 3.26 goals against and .880 save percentage in four games for Canada West, which won a bronze medal at the WHC.
2011-12: Acquired by the Calgary Hitmen in a July 2011 trade, Driedger steadily saw increased time for the Hitmen after beginning the season in a three-man rotation. Appearing in 45 games he finished with a 24-15 record with three shutouts and had a 2.80 goals against and .896 save percentage. Calgary finished second behind WHL champion Edmonton in the Central Division. In the first round playoff series with the Brandon Wheat Kings, 19-year-old Brandon Glover saw the bulk of the action and in two playoff games Driedger was 0-2 with a 6.59 goals against and .813 save percentage. Ranked 13th amongst North American goaltenders in Central Scouting's final rankings prior to the 2012 NHL Draft, he was selected by Ottawa in the third round (76th overall).