Despite missing five games due to injury, Mainor still finished second on the team in sacks for the second straight year with seven, and also added 16 defensive tackles, one tackle for loss, two forced fumbles and one pass knockdown. He recorded two two-sack games and made his only start of the season on Nov 3/12 against the Montreal Alouettes.
Mainor began the season on the practice roster before being inserted into the lineup for the team’s week three matchup against the Calgary Stampeders on Jul 14/11. In his first professional game, Mainor made two defensive tackles, two sacks and blocked one field goal. He would go on to record six sacks in his first four games and finished the season with 22 defensive tackles and eight sacks, which ranked him second on the team. Mainor played in 15 games and made five starts in his rookie season.
Attended training camp with the Calgary Stampeders and recorded four tackles during the preseason.
Signed as a free agent on May 20, 2011
As a senior in college, Mainor had 15 tackles and was leading the team in quarterback hurries with six when his season came to an end due to a knee injury. He was named to the Second-Team All-Sun Belt as a junior after recording 40 tackles – including 9.5 for loss – and five sacks in 10 games.