A 3-star defensive end recruit, Armstrong accepted a football scholarship from the University of Kansas, committing to Kansas over offers from California, Indiana, Iowa State, Michigan State, Purdue, and Texas Tech, among others.[1][2] As a freshman, he appeared in all 12 games and started the last 5 contests at defensive end. He registered 23 tackles, 5 tackles for loss, 3.5 sacks (second on the team), and 4 passes defensed (second on the team).[3]
As a sophomore, he had a breakout season as the starter at left defensive end. He led the team and was second in the conference with 10 sacks, the most by a school player since 2008. He posted 56 tackles (fifth on the team), 20 tackles for loss (fifth in school history), 5 quarterback hurries, 3 forced fumbles, and 2 fumbles recoveries. He had a career-high 11 tackles (3 for loss), 2 sacks, one forced fumble, and one fumble recovery against the University of Texas.
As a junior, his role in the defense changed and his production regressed. He made 63 total tackles (third on the team), 9 tackles for loss, 1.5 sacks, 7 quarterback hurries, 4 passes defensed, 3 forced fumbles, and one fumble recovery.[4] On January 3, 2018, he announced that he would forgo his senior year to enter the 2018 NFL draft.[5] He finished his career with 142 tackles and 15.5 sacks.
Armstrong was selected by the Dallas Cowboys in the fourth round (116th overall) of the 2018 NFL Draft.[8] Armstrong made his first career start on October 14, 2018 against the Jacksonville Jaguars.[9] He recorded his first career sack on November 5, in a game against the Tennessee Titans, a sack he split with Caraun Reid. Entering the league as a 21-year-old rookie, he finished the season with 13 tackles, 8 solo, and a half of a sack, while playing in fifteen of the Cowboys sixteen games (one start).
In 2019, he appeared in 15 games with no starts. He tallied 16 tackles, 2 sacks, 9 quarterback pressures, one forced fumble and 2 special teams tackles. He recorded the first full sack of his career against the Green Bay Packers. He had his first career forced fumble against the New York Giants. He had 5 tackles against the Minnesota Vikings.
In 2020, he appeared in 16 games with 2 starts. He registered 33 tackles (one for loss), 9 quarterback pressures, 2 pass breakups, 2 fumble recoveries and 3 special teams tackles. He had 5 tackles against the Minnesota Vikings. He made 3 defensive tackles, along with one tackle, a forced fumble and a recovered fumble on special teams against the San Francisco 49ers.
In 2021, He appeared in 13 games with five starts, collecting 37 tackles, 5 sacks (third on the team), 22 quarterback pressures (fourth on the team), 2 pass breakups and one fumble recovery that he returned 37 yards for a touchdown. He missed 4 games with a high ankle sprain injury. In Week 2 against the Los Angeles Chargers, he started in place of defensive end Randy Gregory, who was placed on the Reserve/COVID-19 list. In Week 10 against the Atlanta Falcons, he started in place of an injured Randy Gregory, making 3 tackles, one sack, 3 quarterback hurries and one block punt. In the thirteenth game against the Washington Redskins, he had six tackles and returned a fumble recovery 37 yards.
On March 17, 2022, Armstrong signed a two-year contract extension with the Cowboys.[10] He appeared in 17 games with five starts, registering 28 tackles (2 for loss), 8.5 sacks (second on the team), 25 quarterback pressures (fourth on the team), 2 fumble recoveries and 2 blocked kicks. He contributed to replace Gregory in the starting lineup at right defensive end. He had 2 sacks against the Cincinnati Bengals. He made 2 sacks against the Cincinnati Bengals. He blocked a field goal attempt (against the New York Giants and a punt (against the Los Angeles Rams), becoming the sixth in franchise history with multiple blocked punts in his career.
In 2023, he appeared in all 17 games (one start), tallying 28 tackles (7 for loss), 7.8 sacks (second on the team) and 12 quarterback pressures. He had 3 tackles for loss and 2 sacks in the season opener against the New York Giants.
Washington Commanders
On March 14, 2024, Armstrong signed a three-year contract with a maximum value of $45 million with the Washington Commanders.[11][12] He reunited with head coach Dan Quinn, who was his defensive coordinator with the Dallas Cowboys, with the intention of helping to replace defensive ends Montez Sweat and Chase Young.
