Honour Roll

-CFL All-Star, 2017, 2018
-West Division All-Star, 2017, 2018
-Most Outstanding Player, Saskatchewan Roughriders, 2018
-Most Outstanding Defensive Player, Saskatchewan Roughriders, 2018

2016-18: Saskatchewan Roughriders

Jefferson was a defensive force for the Riders in 2018, registering a career-high 10 quarterback sacks and adding 24 defensive tackles, two interceptions — both returned for touchdowns — while forcing two fumbles in 18 games played. In the process, he was named the club’s Most Outstanding Player and Most Outstanding defensive player while being named to both the CFL and West Division All-Star Teams.
He signed with the Blue Bombers as a free agent on February 12, 2019.
Jefferson appeared in all 18 games for the Riders in 2017, posting a career-high 45 tackles with eight sacks and a touchdown. He led the entire CFL in QB pressures in 2017 with 37. Those numbers helped him earn places on both the CFL and West Division All-Star Teams.
Jefferson signed with the Riders on September 28, 2016 after attending training camp with the Washington Redskins. He would appear in five CFL games that fall, registering eight tackles and three sacks.

2014-15: Edmonton Eskimos

Jefferson first came to the Canadian Football League in 2014, signing with the Edmonton Eskimos after being signed by the Houston Texans as an undrafted free agent in 2013 and then being released later that season.
He appeared in 35 regular-season games over two seasons with the Eskimos, picking up 40 tackles and registering 10 sacks while forcing three fumbles. He was part of the Eskimos 2015 Grey Cup championship team.

College

Jefferson began his college career as a receiver at Baylor University before transferring to Stephen F Austin University. He was converted to defensive end there, and was named the  Southland Conference Newcomer of the Year in 2011, his Junior season after leading the conference in sacks with 16.