2009-10: Whitney played for the Valley Sport Swapper Wildcats midget major team in Nova Scotia. The Wildcats finished last in the NSMMHL, winning just 5 of 35 games. Whitney played 27 games and was 3-19-1 with a 6.04 goals against. Whitney was selected by Victoriaville in the third round (51st overall) of the 2010 Quebec Major Junior Hockey League Entry Draft.
2010-11: Whitney appeared in three games with the QMJHL's Victoriaville Tigres – spending most of the season in midget hockey as veterans Antonio Mastropietro and David Honzik split the duties with the Tigres. He was 0-2, allowing 2 goals in just under 26 minutes of action, and finished with a .900 save percentage. Whitney skated in eight games for Taylar Made Titans in the NSMMHL and was 5-3 with a 2.99 goals against and .890 save percentage. Whitney appeared in 8 of 13 playoff games for the Titans and was 5-3 with one shutout and had a 2.26 goals against and .910 save percentage. The Titans advanced to the 2011 Telus Cup national championship but Whitney did not play in the tournament. He represented Canada Atlantic at the 2011 U17 World Hockey Challenge. In four games he was 2-0 with a 3.58 goals against and .898 save percentage.
2011-12: Whitney got off to a fast start, winning his first four QMJHL starts for Victoriaville, and established himself as a legitimate prospect while sharing the goaltending duties with Honzik. He had five straight wins during one December stretch and was 22-8 in 36 appearances, with four of those losses coming in overtime. Whitney had two shutouts and a 2.74 goals against with an .896 save percentage. The Tigres reached the playoffs after finishing second in the East Division and were swept by Baie-Comeau in the first round. Whitney appeared in 3 of 4 playoff games and was 0-2 (including a loss in overtime) with a 5.49 goals against and .831 save percentage. Whitney was chosen for Canada's U18 squad but did not see any action in the 2012 World Junior Championship as Canada captured a bronze medal. He was invited to the NHL Draft Combine and ranked second amongst North American goalies in Central Scouting's final rankings prior to the 2012 NHL Draft.
A huge goalie in the crease, Whitney combines his size with great quickness and athleticism. Like most young goalies, he needs to continue to improve his core strength, which is extra important with such a large frame to help control his movements between the pipes. At times his focus seems to waver and he is guilty of letting a bad goal affect his play, but his natural abilities cannot be ignored. He still needs to continue to refine his technique.
After taking over the reigns for Victoriaville in his rookie year, Whitney enters the 2012-13 season as the starter for the first time in his junior career.