Hitchens recorded five combined tackles and made his first career sack on Philadelphia Eagles' quarterback Sam Bradford during a 20–10 victory. On October 4, 2015, he recorded a season-high 11 combined tackles and sacked Drew Brees in Dallas' 26–20 loss at the New Orleans Saints. On December 19, 2015, Hitchens started at middle linebacker in place of Rolando McClain who suffered an injury and collected ten combined tackles during a 19–16 loss to the New York Jets. He finished the season with a total of 67 combined tackles (40 solo), two sacks, and a defended pass in 16 games and nine starts as the Cowboys finished 4–12. His production was slightly decreased due to the return of Sean Lee. 2016 Hitchens began training camp competing with Kyle Wilber and Damien Wilson for the role as the strongside linebacker. He took over the role as the Cowboys' starting middle linebacker after Rolando McClain was dealt a ten-game suspension after violating the performance-enhancing drugs policy. He started the Dallas Cowboys' season-opener at the New York Giants and collected six combined tackles in their 20–19 loss. On December 1, 2016, Hitchens recorded a season-high ten combined tackles, deflected a pass, and sacked Minnesota Vikings' quarterback Sam Bradford, as the Cowboys won 17–15. He finished the season with 78 combined tackles (39 solo), 1.5 sacks, and a pass deflection in 16 games and 16 starts. The Dallas Cowboys received a playoff berth after finishing atop the NFC East with a 13–3 record. On January 15, 2017, Hitchens started his first career playoff game and collected seven combined tackles in a 34–31 loss at the Green Bay Packers in the NFC Divisional Round. 2017 He received a considerable raise for the season after playing over 35% of the Dallas Cowboys' defensive snaps. His salary went from $690,000 to $1.84 million after qualifying for the Proven Performance Escalator. The Proven Performance Escalator was added to the rookie wage scale as a part of the collective bargaining agreement in and applies to players who were drafted in the third to seventh round. Throughout training camp in , Hitchens competed with Jaylon Smith to maintain his role as the starting middle linebacker. Hitchens was slated to start the season at middle linebacker, but suffered a tibial plateau fracture in the Dallas Cowboys' final preseason game against the Oakland Raiders. He was expected to miss up to eight weeks,