Butler played college football for the University of Memphis, starting for three years at inside linebacker. He had 384 career tackles and seven interceptions, leading the school in tackles during his junior and senior seasons. Butler was named a 1977 Associated Press All-American in his senior year, playing in the Senior Bowl and the Blue-Gray All-Star Game.
Butler was selected 36th overall by the Seattle Seahawks in the 1978 NFL Draft. He started 132 of 146 games in his 10-year career, and finished with 813 tackles (ranking second on the Seahawks' all-time tackles list).
Butler began his coaching career at Memphis in 1990, coaching linebackers and later expanding his role to cover defensive ends and special teams by 1997. He was the architect of a surprise 3-4 defensive scheme which led to Memphis' shocking 1996 upset of the #6 Tennessee Volunteers, led by junior quarterback Peyton Manning. He then moved to Arkansas State in 1998 to serve as defensive coordinator and linebackers coach.
His professional coaching debut came as a linebackers coach for the expansion Cleveland Browns in 1999. He was the only assistant coach retained after a staff turnover in 2001 and coached the next two seasons under Butch Davis, mentoring the expansion club's first ever Pro Bowl selection, linebacker Jamir Miller.
Butler moved to the Pittsburgh Steelers in 2003, serving as linebackers coach. He has been instrumental in mentoring the development of the Steelers' renowned linebacking corps. His linebacker experience helped the Steelers consistently lead the NFL in rushing defense, total defense, and sacks between 2004-2012. Butler has been influential in the development of Pro Bowl linebackers Joey Porter, James Farrior, Lawrence Timmons, LaMarr Woodley, and James Harrison. Harrison, in particular, improved from an undrafted practice squad linebacker into the NFL Defensive Player of the Year under Butler's tutelage.
During his twelve-year tenure as the Steelers' linebackers coach, Butler was considered the heir-apparent for the defensive coordinator position held by the respected Dick LeBeau. Following LeBeau's resignation, Butler was promoted to defensive coordinator on January 13, 2015. The Steelers defense was vastly improved in Butler's first season, increasing their sack total from the prior season 33 to 48, increasing their turnovers from 21 to 30, decreasing their points allowed by 4 per game, and leading the NFL in red zone turnovers.
Butler married his wife Janet in 1980 and together they have three adult sons, Blake, Brandon, and Brett. Both Blake and Brandon played college football: Blake played offensive line for the University of Memphis from 2002 until 2006, and Brandon played linebacker/defensive end for the University of Akron from 2003 until 2006, and later at Ashland University during the 2007 and 2008 seasons.