As a senior linebacker in 2011, Morrison was named 1st Team All-State after leading Bolingbrook to an IHSA Class 8A State Championship.

[2] On January 3, 2015, Morrsion played in the 2015 Birmingham Bowl, but left the Gators 28–20 victory over East Carolina in the second quarter after he suffered a knee injury while making a tackle.

[6] On January 30, 2016, Morrison played in the Reese's Senior Bowl and was part of Jacksonville Jaguars head coach Gus Bradley's South team that defeated the North 27–16.

[8] On March 22, 2016, Morrison attended Florida's pro day and performed all of the combine and positional drills as over 70 scouts and representatives from all 32 NFL teams looked on.

[9] Morrison also attended private workouts and visits with a few teams, including the Buffalo Bills, Tennessee Titans, and Chicago Bears.

[10][11][12] At the conclusion of the pre-draft process, Morrison was projected to be a seventh round pick or priority undrafted free agent by the majority of NFL draft experts and scouts.

[19][20] Throughout training camp, Morrison competed against Sio Moore, Nate Irving, Amarlo Herrera, Junior Sylvestre, and Edwin Jackson in an open competition for the vacant starting inside linebacker role after Jerrell Freeman departed during free agency.

[21][22] Head coach Chuck Pagano named Morrison the fourth inside linebacker on the depth chart to begin the regular season, behind D'Qwell Jackson, Moore, and Josh McNary.

Morrison made his first career tackle on tight end Eric Ebron after he caught a 13-yard pass from Matthew Stafford in the second quarter.

[29] Defensive coordinator Ted Monachino stated the Colts would hold an open competition during organized team activities and training camp to name a new starting inside linebackers to replace longtime veteran D'Qwell Jackson, who was released after the 2016 season.

The competition included Morrison, Jon Bostic, Sean Spence, Luke Rhodes, Edwin Jackson, and rookie Anthony Walker Jr.[30][31] Head coach Chuck Pagano named Morrison and Jon Bostic the starting inside linebackers, along with outside linebackers John Simon and Jabaal Sheard.