PITTSBURGH (AP) — His flowing locks bouncing off the top of his No. 43 jersey, Troy Polamalu spent more than a decade flying across football fields as the heady but humble backbone of a defense that fueled the Pittsburgh Steelers’ return to the NFL’s elite.

Now, his singular career is a part of franchise lore. Move over Joe Greene, Jack Lambert and Mel Blount. You’ve got company.

Polamalu, an eight-time Pro Bowler and 2010 NFL Defensive Player of the Year, is retiring after 12 seasons, telling the only team he’s ever played for that it’s time for the next phase of his life. Polamalu’s retirement was first reported by the Uniontown (Pa.) Herald-Standard.

“Troy is a shining example of a football man in the way he loved the game, the way he respected the game and the way he played the game,” Steelers coach Mike Tomlin said in a statement. “It’s a shining example of the window into who he is. He is a legendary Steeler and a legendary man.”

Taken with the 16th overall pick in the 2003 NFL draft out of USC, Polamalu’s frenetic style and preternatural instincts allowed him to thrive in Hall of Fame defensive coordinator Dick LeBeau’s 3-4 defense. At his peak, Polamalu was arguably the most disruptive player in the league. His ability to anticipate what was coming became highlight fodder that will live on for generations, whether he was leaping over the line of scrimmage while trying to stuff a quarterback sneak or feathering his fingertips under the ball to pluck a pass before it struck the ground.

Still, beneath the hair that earned him a lucrative endorsement deal and the splash plays that changed the course of seasons — including a pick-six against Baltimore in the 2008 playoffs that paved the way for the team’s sixth Super Bowl title — was a man who defined himself as more than just a football player. He was open about his deep Christian faith and made the sign of the cross gesture following tackles.

Soft-spoken and thoughtful, Polamalu’s quiet nature away from the game played in stark contrast to the hell-bent way he went about his job. He embraced the role of mentor late in his career, taking expected successor Shamarko Thomas under his wing two years ago, even inviting Thomas to train with him on the west coast last spring, a regimen that Thomas joked was akin to learning how to be a ninja.

“His actions as a human being were just as impressive as any of the many inhuman plays he made on the football field,” Steelers general manager Kevin Colbert said. “We were very fortunate to have him be a part of our organization for the past 12 years.”

Polamalu finishes with 32 career interceptions, a dozen sacks, seven fumble recoveries and five touchdowns. The numbers, however, hardly do justice to the way Polamalu could wreak havoc on opposing game plans. LeBeau loved to say simply “Troy will be Troy” when asked how the Steelers might use Polamalu on a given Sunday.

While LeBeau’s system relied heavily on discipline and disguise, Polamalu was given expansive freedom to go where he felt the ball was headed. He was right more often than he was wrong. Yet his relentless play took a toll on his sturdy but hardly chiseled 5-foot-10, 213-pound frame. He played a full 16-game schedule just twice in his final six seasons, missing more than half of 2012 with calf problems and four games in 2014 following a fluky knee injury. Polamalu returned in time for Pittsburgh’s loss to Baltimore in the wild-card round of the playoffs, registering five tackles in what turned out to be his final game.

Polamalu, who had two years remaining on his contract with the Steelers, said in the aftermath of the loss he would have to wait and see what the future held.

Polamalu told the Herald-Standard he never considered playing for another team and decided it was time to move on when he wondered if he could make the commitment necessary to play another season.

His departure marks the third significant shake-up for a defense in transition during a busy offseason. LeBeau left in January after not having his contract renewed and free agent linebacker Jason Worilds abruptly retired in March at age 27.

LeBeau landed a job with Tennessee and Worilds is young enough that a comeback isn’t out of the question. Not so with Polamalu, who could become the first member of the core group that led the Steelers to two Super Bowl wins and three appearances in six seasons to be enshrined in the Pro Football Hall of Fame.

Tributes came pouring in through social media in the aftermath of Polamalu’s announcement, with opponents who spent long Sunday afternoons dreading dealing with Polamalu tipping their caps in reverence to an iconic career.

Tim Tebow tweeted Polamalu was one of the “toughest, smartest and kindest players I played against” while San Francisco wide receiver Torrey Smith — who tangled regularly with Polamalu while playing for the Ravens — tweeted “Polamalu would do some crazy things on the football field....loved watching him play and competing against him.”

It’s a feeling echoed by nearly all that witnessed Polamalu’s freakish talent in person.

“We’ve been fortunate to have great players throughout the years, but he of course would be one of the top players,” Steelers chairman Dan Rooney said. “He did everything with dignity and responsibility, and it was special to have Troy be a Steeler his entire career.”