He also played for the New York Jets.
Marshall was born in Pineview, Georgia, the son of Phillip Marshall and Shalina Cliett, and attended high school at Wilcox County High School in Rochelle, Georgia. He was a three-sport star in basketball, football and track. He was named the boys basketball AP Class A player of the year twice. In football, he led Wilcox County to the Class A championship as a junior, while passing for 2,956 yards and 32 touchdowns. He was named the Class A Offensive Player of the Year as well as a part of the PrepStar All-American team, SuperPrep All-Dixie team, and Atlanta Journal-Constitution "Super 11" team. 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. At the Georgia Class A State Meet, he finished fifth in the high jump, recording a career-best leap of 1.93 meters (6-4). After that meet, he never competed in track again.
Marshall decided on going to the University of Georgia for college because he was offered the opportunity to play both basketball and football.
Marshall began his college career in 2011 as a cornerback for the University of Georgia. Marshall and two teammates were dismissed from the team for an unspecified "violation of team rules."
Marshall transferred to Garden City Community College where he was the starting quarterback in 2012 and led the team to a 7–4 record while scoring 37 touchdowns (19 rushing, 18 passing), passing for 3,142 yards, and becoming the team’s leading rusher with 1,095 yards. After one season with Garden City Community College, Marshall then transferred to Auburn with the hope of playing quarterback.
In August 2013, Marshall was named starting quarterback for Auburn. 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.
Marshall was instrumental in Auburn's turnaround from a 3–9 season in 2012 to beginning the 2013 season 9–1 while beating the Ole Miss Rebels, then ranked #24 in the AP Poll and #6 Texas A&M Aggies.
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 to defeat the Georgia Bulldogs.
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. Auburn won the game on a 109-yard touchdown return from an Alabama missed field goal. The team later went on to win the SEC Championship, and earned a berth in the 2014 BCS National Championship Game and lost.
After his time at Auburn, he decided to enter the 2015 NFL Draft.
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.
Marshall was signed by the Jacksonville Jaguars as a free-agent after going undrafted in the 2015 NFL Draft He played primarily on special teams including returning kickoffs for most of the season but saw his role on defense increase the last four weeks of the season. He started his first NFL game week 17 against the Houston Texans. On September 3, 2016, he was released by the Jaguars. He was signed to the Jaguars' practice squad the next day.
On October 12, 2016, Marshall was signed by the Jets off of the Jaguars' practice squad.
On April 14, 2017, Marshall was suspended four games for testing positive on performance-enhancing drugs. Marshall was waived by the Jets on May 4, 2017.