Mark J. Rebilas, Mark J. Rebilas-USA TODAY Sports

Longtime Steelers defensive coordinator Keith Butler announced his retirement on Saturday. A linebacker with the Seahawks from 1978-87, Butler began his coaching career in 1990. He spent 19 seasons with the Steelers that included the last seven seasons as Pittsburgh's defensive coordinator. 

"It is an emotional day as I announce I am retiring from my football coaching career," said Butler. "I have spent every year since 1990 as a coach in the NFL and the NCAA, but the time is right for me to walk away after a successful career both playing and coaching the game I love.

"I want to thank the Rooney Family, Bill Cowher, Mike Tomlin and all the coaches and players that I have been involved with over my entire coaching career. I look forward to spending more time with my family, whom have been so supportive of me throughout the years. I wish nothing but the best to the Pittsburgh Steelers, and I will be cheering them on during my retirement."

Under Butler, the Steelers' defense led the NFL in sacks in each of the last five seasons. Defenders T.J. Watt, Cameron Heyward and Minkah Fitzpatrick have flourished under Butler, who won two Super Bowls as the team's linebackers coach from 2003-14. One of the Steelers' best players during Butler's time as Pittsburgh's linebackers coach was outside linebacker James Harrison, who Defensive Player of the Year honors in 2008. Harrison capped off that season with a 100-yard interception return for a score in Pittsburgh's 27-23 win over Arizona in Super Bowl XLIII. 

Butler served on Memphis' coaching staff from 1990-98. During the 1996 season, Butler worked with a young graduate assistant named Mike Tomlin, who retained Butler on his coaching staff upon being named the Steelers head coach in 2007. 

"I had his football card when I was a kid," Tomlin said of Butler in 2015. "And one of the first times we met, when I first got hired at Memphis as a [graduate assistant], I said, 'Man, you're No. 53 from Seattle with the beard.'"

Before coming to Pittsburgh, Butler served as the linebackers coach in Cleveland from 1999-02. During his final season with the Browns, Cleveland clinched its first playoff berth since returning to the NFL behind a defense that finished 10th in the NFL in scoring. Ironically, the Browns' season ended with a wild card loss to the Steelers, who hired Butler to be their new linebackers coach heading into the 2003 season. A dozen years later, he succeeded longtime Pittsburgh defensive coordinator Dick LeBeau. 

The Steelers' best team finish during Butler's time as defensive coordinator was in 2016, when Pittsburgh won nine straight games to advance to the AFC Championship Game. The Steelers' defense held the Dolphins and Chiefs to a combined 28 points in the first two rounds of the playoffs. 

Pittsburgh had 12 playoff appearances during Butler's time with the Steelers, who are also preparing to lose quarterback Ben Roethlisberger and longtime general manager Kevin Colbert this offseason.

Teryl Austin is among the candidates to replace Butler. Austin, who won a Super Bowl in 2012 as the Ravens' secondary coach, has been the Steelers' senior defensive assistant/secondary coach for the past three seasons.