Gordon began his professional career being named the starting running back for the Chargers' season opener, ahead of veterans Danny Woodhead and Branden Oliver. On September 13, 2015, he received his first career start against the Detroit Lions and finished the season opener with 14 carries, 51 rushing yards, three receptions, 16 receiving yards, and lost a fumble. The next week, he carried the ball 16 times for a season-high 88 yards and made a 10-yard reception in a 24–19 loss at the Cincinnati Bengals. On October 12, 2015, Gordon had seven catches for a season-high 52 yards and also accounted for 42 yards on 15 carries in a 20–24 loss to the Pittsburgh Steelers.  During a Week 6 matchup at the Green Bay Packers, he had seven attempts for 29 yards and lost two fumbles in a 20–27 loss.  After six consecutive starts to begin his career, Gordon was benched for the beginning of a Week 7 contest against the Oakland Raiders. He finished the game with seven carries for 29 yards.  Gordon returned to his starting role the next game at the Baltimore Ravens and carried the ball a season-high 18 times for 54 yards in a 26–29 loss.  In his last game of the season, he had 15 rushing attempts and 41-yards in a 30–14 victory over the Miami Dolphins.