As a freshman, he joined the school's track & field team, and with only two weeks of training, he qualified for the state finals in the high jump by leaping 1.78 meters (5-10) at the Region 2A Boys Meet.

[6] After one season with Garden City Community College, Marshall then transferred to Auburn with the hope of playing quarterback.

[7] This came after a heated four-man race for the position in head coach Gus Malzahn's newly installed offense which saw 2012 starting quarterback Kiehl Frazier transfer to safety on the defensive side of the ball.

On November 16, 2013, Marshall was the quarterback behind a play known as "The Prayer at Jordan-Hare" when he threw a 73-yard Hail Mary touchdown pass to Ricardo Louis on a 4th-and-18 with 36 seconds left[9] to defeat the Georgia Bulldogs.

[10] On November 30, 2013, Marshall threw the game-tying touchdown pass with 32 seconds remaining in the epic 2013 Iron Bowl to even the score 28–28.

[12] Although he was invited to the 2015 Senior Bowl as a quarterback, Marshall announced during the week that he would move to cornerback in his attempt for an NFL career.

[26] In Week 1 against the Toronto Argonauts, Marshall recorded an interception for a touchdown for the game-winning points in the 27–19 victory, but was subsequently placed on the six-game injured list following a broken finger.

[28] Marshall has subsequently been used as a situational rusher on short yardage and goal-line plays, recording 18 rushes for 48 yards and 7 touchdowns.

In 13 games, Marshall finished the regular season with 26 tackles, 3 interceptions (two of which were returned for scores), and one forced fumble.