Murphy recorded his first career interception of a pass made by Keith Price, resulting in a 40-yard return for a touchdown.

[28] Also for the second year running, Murphy received Stanford's Jack Huston Award, voted by his peers as the player exemplifying aggressiveness, exceptional performance and unheralded efforts.

[52] Murphy was regarded as one of the top defenders in college football, but was seen as a disappointment by a media member during Senior Bowl practices.

[53] On January 25, 2014, Murphy played in the Reese's Senior Bowl and made four combined tackles as a part of Atlanta Falcons head coach Mike Smith's North team that lost 20–10 to the South.

[58] Murphy was seen as a long-term solution for the possible departure of Brian Orakpo, who was franchise tagged and was designated to be a free agent after 2014.

[60][61] He entered training camp slated as the backup outside linebacker to veterans Ryan Kerrigan and Brian Orakpo.

Head coach Jay Gruden officially named him the backup right outside linebacker to Orakpo to start the regular season.

[65] In Week 9, Murphy recorded four combined tackles and made his first career sack on quarterback Teddy Bridgewater as the Redskins lost 29–26 versus the Minnesota Vikings.

The following week, he made his eighth consecutive start, but left the 27–24 win over the Eagles after suffering a hand injury.

On December 23, 2014, the Washington Redskins placed Murphy on injured reserve after it was discovered he had fractured a bone in his right hand.

[68] Murphy entered training camp in 2015 as the Redskins' starting strongside linebacker following the departure of Brian Orakpo to the Tennessee Titans in free agency.

On November 15, 2015, Murphy recorded a season-high five combined tackles and was credited with a half a sack on Drew Brees during a 47–14 victory over the New Orleans Saints.

During a Week 13 matchup against the Chicago Bears, he made one solo tackle and had the first forced fumble of his career in their 24–21 victory.

[70] Murphy finished the 2015 season with 33 combined tackles (13 solo), 3.5 sacks, and a forced fumble in 14 starts and 16 games.

[72][73] On August 8, 2016, it was reported that the move to defensive end was cancelled after Junior Galette, who was taking over the starting strongside linebacker role, suffered an achilles injury.

[74] Head coach Jay Gruden named Murphy the backup strongside linebacker behind Preston Smith to start the regular season.

[77] On October 2, 2016, he made a season-high five solo tackles and sacked Cody Kessler during the Redskins' 31–20 win over the Cleveland Browns.

Murphy recorded his first career interception during Week 2 of the 2019 season, catching a tipped Eli Manning pass during a 28–14 Bills win over the Giants.