2007-08: Chosen in the first round of the 2008 OHL Priority Selection by the Windsor Spitfires. Named a first-team tournament All-Star at the 2008 World U-17 Hockey Challenge, in London, Ontario.
2008-09: Played for the U.S. NTDP U-18 team. Earned a gold medal at the 2008 Men’s Under-18 Four Nations Cup, leading all defensemen in that tournament in scoring. Also earned a gold medal as a member of Team USA’s entry at the
2009-10: In his OHL rookie season, Fowler played in 55 games for the Windsor Spitfires. He scored 8 goals and added 47 assists for 55 points while posting a +38 rating for the season. In 19 playoff games, Fowler scored 3 goals and added 11 assists for 14 points as he and his Spitfires’ teammates won the OHL championship for the second consecutive year. Fowler won a gold medal as a member of the Team USA squad that won the Under-20 2010 World Junior Championships. He played for Team Cherry at the 2010 CHL Top Prospects Game.