Following the 2015 NFL Draft, he was signed as an undrafted free agent by the Jacksonville Jaguars of the National Football League (NFL). He was a quarterback for Auburn from 2013 to 2014 and was the Tigers' starting quarterback. As a freshman in 2013, he led Auburn to its first win over Alabama since 1981 when he threw for 347 yards and three touchdowns in a 42-35 victory over the Crimson Tide. He transferred to Miami (OH) after one season at Auburn. As a sophomore in 2015, he started eight games for the Hurricanes before being sidelined with an injury. He passed for 2,996 yards and 21 touchdowns and rushed for another 1,010 yards and 11 scores. After his successful run at Miami (OH), where he finished second in Heisman voting as a quarterback in 2015, Marshall was drafted by the Jacksonville Jaguars in the seventh round (242nd overall pick) of the 2016 NFL Draft. Auburn head coach Gus Malzahn said following the draft that if Marshall decided to switch positions he would be able to make an immediate impact with the Jaguars. "If he wanted to go into defense, I think he'd be able to do some good things there," Malzahn said. "I know they need help at both corner spots, so maybe running back or defensive end. Those are two positions of need for them."