Riley played at LSU from 2013 to 2016. After spending his first three seasons as a backup, he became a starter for the first time his senior year in 2016. That season, he had 93 tackles, 1.5 sacks, and one interception and was named the teams MVP.
Professional career
On November 16, 2016, it was reported that Riley had accepted an invitation to play in the Reese's Senior Bowl, joining LSU teammates Tre'Davious White, Ethan Pocic, Travin Dural, and Kendell Beckwith. On January 2, 2017, it was announced by Lil' Wayne on Instagram that Riley had signed with his company Young Money APAA Sports, and had successfully merged with his Young Money Entertainment record label. He became the company's first client they represented. He had an impressive week of practices at the Senior Bowl under Cleveland Browns' head coach Hue Jackson, showing athleticism, quick instincts, and range. On January 28, 2017, Riley recorded a team-high seven combined tackles, helping the South defeat the North 16-15. His overall performance was spectacular during the 2017 Senior Bowl and was thought to immensely improve his draft stock. He received an invitation to the NFL Combine and completed nearly all of the required drills, but opted to skip the short shuttle and three-cone drill. On April 5, 2017, Riley participated at LSU's pro day, but opted to stand on his combine numbers and only perform positional drills. Over 125 team representatives and scouts attended, including head coachesSean Payton, Mike Tomlin, Mike Mularkey, Todd Bowles, and Jim Caldwell. Riley opted to run the 40-yard dash, 20-yard dash, and 10-yard dash again while also performing positional drills. At the conclusion of the pre-draft process, Riley was projected to be a second to fourth round pick by the majority of NFL draft experts and scouts. He was ranked the seventh best outside linebacker by NFLDraftScout.com.
The Atlanta Falcons selected Riley in the third round of the 2017 NFL Draft. He was reunited with former LSU teammate Deion Jones who Riley looked at as a role model as an elite linebacker at LSU. Riley also wore number 0 at the Senior Bowl to hopefully begin a tradition that began with Jones when he was the first player to wear the number 0 in a Senior Bowl. On May 11, 2017, the Atlanta Falcons signed Riley to a four-year, $3.51 million contract that includes a signing bonus of $889,752. Throughout training camp, Riley competed with De'Vondre Campbell, Josh Keyes, J'Terius Jones, and Jermaine Grace for the starting weakside linebacker position. Head coach Dan Quinn named him the backup weakside linebacker to veteran De'Vondre Campbell to begin the season. He earned his first start in the Atlanta Falcons' season-opener against the Chicago Bears and made six combined tackles in the 24-17 victory. Riley earned his first career start at weakside linebacker with De'Vondre Campbell starting at the strongside linebacker position over Vic Beasley. Duke Riley, De'Vondre Campbell, and Deion Jones were the starting linebacker corp in the Atlanta Falcons' big base package. Unfortunately, Riley missed four tackles during the game, but played 49 out of 67 defensive snaps. On October 22, 2017, Riley recorded a solo tackle in a 7-23 loss to the New England Patriots, but left the game after tearing his meniscus. He underwent successful surgery to repair the tear and missed the next four games. He finished his rookie season in 2017 with 30 combined tackles in 12 games and six starts. The Atlanta Falcons finished third in the NFC South with a 10–6 record and earned a wildcard berth. On January 6, 2018, Riley appeared in his first career playoff game and made two combined tackles during a 26–13 victory at the Los Angeles Rams in the NFC Wild Card Round. The following week, he made one tackle as the Falcons lost 15–10 in the NFC Divisional Round to the Philadelphia Eagles.
2018
Riley had a disappointing 2018 campaign, and saw his role diminish throughout the season. Initially Riley entered training camp slated as the starting weakside linebacker, but saw minor competition for the role from Foyesade Oluokun, who ended up surpassing Riley on the depth chart. Head coach Dan Quinn named Riley the starting weakside linebacker to begin the regular season. He started the season alongside De’Vondre Campbell and middle linebacker Deion Jones. In Week 3, he collected a season-high 13 combined tackles during a 43-37 loss against the New Orleans Saints. Riley began seeing a decreased snap count during the season and eventually lost his starting role to Foyesade Oluokun in Week 13 and remained a backup for the remainder of the season. He finished the season with 60 combined tackles and two pass deflections in 16 games and ten starts. He received an overall grade of 44.2 from Pro Football Focus, which ranked 87th among all qualifying linebackers in 2018.
Philadelphia Eagles
On September 30, 2019, Riley was traded to the Philadelphia Eagles for safety Johnathan Cyprien and a swap of late-round picks. On January 2, 2020 Riley was named special teams captain for the Eagles Wild card match up with Seattle.
