Ryans played college football for the Alabama Crimson Tide, where he was named a unanimous All-American.

Ryans was selected by the Texans in the second round of the 2006 NFL draft, where he was recognized as the Defensive Rookie of the Year.

Ryans was selected to two Pro Bowls before being traded to the Philadelphia Eagles in 2012, where he spent four seasons before retiring.

Ryans was hired as the head coach for the Texans in 2023, taking the team to the playoffs in his first season in that role.

[5][6] Ryans started his career by earning a role on special teams and backup linebacker in his first season.

Ryans was named the 2006 Cotton Bowl Classic defensive MVP in their 13–10 win over Texas Tech.

[8] Following his senior season, Ryans received the Lott Trophy for his combination of athletic excellence and off-the-field achievements and was recognized as a unanimous All-American.

[32] On January 18, 2021, Ryans was promoted to defensive coordinator following the departure of Robert Saleh, who left to become the head coach of the New York Jets.

[37] On January 31, 2023, Ryans was hired as head coach of the Houston Texans, the same franchise he started his professional NFL career for, after signing a six-year contract.

[40] However, under Ryans' leadership, the team finished atop the AFC South with a 10–7 record and made the playoffs.